27 solved
Co-authored-by: sigonasr2 <sigonasr2@gmail.com>
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archives/27/current
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archives/27/current
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66
archives/27/src/main.c
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66
archives/27/src/main.c
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#include <stdio.h>
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#include "utils.h"
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/*
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Euler discovered the remarkable quadratic formula:
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It turns out that the formula will produce 40 primes for the consecutive integer values . However, when is divisible by 41, and certainly when is clearly divisible by 41.
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The incredible formula was discovered, which produces 80 primes for the consecutive values . The product of the coefficients, −79 and 1601, is −126479.
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Considering quadratics of the form:
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, where and
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where is the modulus/absolute value of
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e.g. and
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Find the product of the coefficients, and , for the quadratic expression that produces the maximum number of primes for consecutive values of , starting with .
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https://projecteuler.net/problem=27
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*/
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int main(int argc,char**argv) {
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FILE*f = fopen("archives/primegenerator/primes","r");
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int startMarker=0;
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while (fgetc(f)!='{') {
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startMarker++;
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}
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int primes[2500];
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char c;
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int counter=0;
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while (counter<2500) {
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int digit=0;
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while ((c=fgetc(f))!=',') {
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digit*=10;
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digit+=c-'0';
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}
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primes[counter++]=digit;
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}
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int n=0;
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int maxLength=0;
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int maxA=0;
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int maxB=0;
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for (int a=-999;a<1000;a++) {
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for (int b=-999;b<=1000;b++) {
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for (int p=0;p<2500;p++) {
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if (n*n+a*n+b==primes[p]) {
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n++;
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p=0;
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}
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}
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if (n>maxLength) {
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maxLength=n;
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maxA=a;
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maxB=b;
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printf("New max of %d found with n^2+%dn+%d\n",maxLength,maxA,maxB);
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}
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n=0;
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}
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}
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printf("\n\nProduct of maxes (%d*%d)=%ld\n",maxA,maxB,(long)maxA*maxB);
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return 0;
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}
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173
archives/27/src/utils.c
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173
archives/27/src/utils.c
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#include "utils.h"
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#include <stdio.h>
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#include <stdlib.h>
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struct String mult(struct String numb1, struct String numb2) {
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struct String n1 = numb1;
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struct String n2 = numb2;
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byte carryover = 0;
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if (numb2.length>numb1.length) {
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n1=numb2;
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n2=numb1;
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}
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int addends[n2.length][n1.length+1];
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for (int i=0;i<n2.length;i++) {
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for (int j=0;j<n1.length+1;j++) {
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addends[i][j]=0;
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}
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}
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for (int i=n2.length-1;i>=0;i--) {
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carryover=0;
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for (int j=n1.length-1;j>=0;j--) {
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int mult = (n1.str[j]-'0')*(n2.str[i]-'0')+((carryover!=0)?carryover:0);
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//printf(" %d/%d\n",mult,carryover);
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carryover=0;
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if (mult>=10) {
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carryover=mult/10;
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mult=mult%10;
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}
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addends[(n2.length-1)-i][j+1]=mult;
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}
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if (carryover>0) {
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addends[(n2.length-1)-i][0]=carryover;
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}
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}
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//printIntDoubleArr(n2.length,n1.length+1,addends);
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struct String sum = {1,"0"};
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for (int i=0;i<n2.length;i++) {
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char val[n1.length+1+i];
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for (int j=0;j<n1.length+1+i;j++) {
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val[j]='0';
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}
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for (int j=0;j<n1.length+1;j++) {
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val[j]=addends[i][j]+'0';
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}
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sum=add((struct String){n1.length+1+i,val},sum);
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//printf("%s\n",sum.str);
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}
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if (sum.str[0]=='0') {
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char*newStr=malloc(sum.length-1);
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for (int i=1;i<sum.length;i++) {
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newStr[i-1]=sum.str[i];
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}
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free(sum.str);
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sum=(struct String){sum.length-1,newStr};
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}
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//printf("%s",sum.str);
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return sum;
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}
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struct String add(struct String numb1, struct String numb2){
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//printf("%s %s\n",numb1.str,numb2.str);
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byte carryover=0;
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int digitCount=0;
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char*str = malloc(1);
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//str[0]='\0';
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if (numb1.length>=numb2.length) {
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for (int offset=0;offset<numb1.length;offset++) {
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str = realloc(str,++digitCount);
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//printf("Digit count is now %d\n",digitCount);
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if (numb2.length>offset) {
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//printf("%c %c\n",numb1.str[numb1.length-offset-1],numb2.str[numb2.length-offset-1]);
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int sum=((numb1.str[numb1.length-offset-1]-'0')+(numb2.str[numb2.length-offset-1]-'0'))+((carryover>0)?carryover--:0);
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if (sum>=10) {
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carryover=1;
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sum-=10;
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}
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str[offset]=sum+'0';
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} else {
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str[offset]=numb1.str[numb1.length-offset-1]+((carryover>0)?carryover--:0);
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}
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//str[offset+1]='\0';
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}
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} else {
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for (int offset=0;offset<numb2.length;offset++) {
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str = realloc(str,++digitCount);
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//printf("Digit count is now %d\n",digitCount);
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if (numb1.length>offset) {
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//printf("%c %c\n",numb1.str[numb1.length-offset-1],numb2.str[numb2.length-offset-1]);
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int sum=((numb1.str[numb1.length-offset-1]-'0')+(numb2.str[numb2.length-offset-1]-'0'))+((carryover>0)?carryover--:0);
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if (sum>=10) {
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carryover=1;
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sum-=10;
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}
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str[offset]=sum+'0';
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} else {
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str[offset]=numb2.str[numb2.length-offset-1]+((carryover>0)?carryover--:0);
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}
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//str[offset+1]='\0';
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}
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}
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if (carryover>0) {
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str = realloc(str,++digitCount);
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str[digitCount-1]='1';
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//str[digitCount]='\0';
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}
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for (int i=0;i<digitCount/2;i++) {
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char c = str[i];
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char c2 = str[digitCount-i-1];
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str[digitCount-i-1]=c;
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str[i]=c2;
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}
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str = realloc(str,digitCount+1);
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str[digitCount]='\0';
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struct String newStr = {digitCount,str};
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return newStr;
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}
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void printLongDoubleArr(int a,int b,long doubleArr[a][b]) {
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for (int i=0;i<a;i++) {
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for (int j=0;j<b;j++) {
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printf("%ld\t",doubleArr[i][j]);
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}
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printf("\n");
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}
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}
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void printIntDoubleArr(int a,int b,int doubleArr[a][b]) {
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for (int i=0;i<a;i++) {
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for (int j=0;j<b;j++) {
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printf("%d\t",doubleArr[i][j]);
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}
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printf("\n");
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}
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}
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struct String createBigNumber(char*numb) {
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int marker=0;
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while (numb[marker++]!='\0');
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return (struct String){marker-1,numb};
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}
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int*getFactors(int numb) {
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int*factorList=malloc(sizeof(int)*1);
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int factorListSize=2;
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factorList[0]=1;
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factorList[1]=numb;
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int max=numb;
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for (int i=2;i<max;i++) {
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if (numb%i==0) {
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factorList=realloc(factorList,sizeof(int)*++factorListSize);
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factorList[factorListSize-1]=i;
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if (numb/i!=i) {
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factorList=realloc(factorList,sizeof(int)*++factorListSize);
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factorList[factorListSize-1]=numb/i;
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max=numb/i;
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}
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}
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}
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factorList=realloc(factorList,sizeof(int)*++factorListSize);
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factorList[factorListSize-1]=0;
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return factorList;
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}
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boolean isFactor(int*factorList,int numb) {
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int counter=0;
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while (factorList[counter]!=0) {
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if (numb==factorList[counter]) {
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return true;
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}
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counter++;
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}
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return false;
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}
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16
archives/27/src/utils.h
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16
archives/27/src/utils.h
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#define true 1
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#define false 0
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#define boolean char
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#define byte char
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struct String{
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int length;
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char*str;
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};
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struct String add(struct String numb1, struct String numb2);
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struct String mult(struct String numb1, struct String numb2);
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void printLongDoubleArr(int a,int b,long doubleArr[a][b]);
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void printIntDoubleArr(int a,int b,int doubleArr[a][b]);
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struct String createBigNumber(char*numb);
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#define BigNumber(X) createBigNumber(#X)
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boolean isFactor(int*factorList,int numb);
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int*getFactors(int numb);
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34
src/main.c
34
src/main.c
@ -26,15 +26,41 @@ int main(int argc,char**argv) {
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while (fgetc(f)!='{') {
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startMarker++;
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}
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fseek(f,startMarker,SEEK_SET);
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int primes[2500];
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char c;
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int counter=0;
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while (counter<2500) {
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int digit=0;
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while ((c=fgetc(f))!=',') {
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digit*=10;
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digit+=c-'0';
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}
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primes[counter++]=digit;
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}
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int n=0;
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while (true) {
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for (int a=1;a<1000;a++) {
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for (int b=1;b<=1000;b++) {
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int maxLength=0;
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int maxA=0;
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int maxB=0;
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for (int a=-999;a<1000;a++) {
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for (int b=-999;b<=1000;b++) {
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for (int p=0;p<2500;p++) {
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if (n*n+a*n+b==primes[p]) {
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n++;
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p=0;
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}
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}
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if (n>maxLength) {
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maxLength=n;
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maxA=a;
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maxB=b;
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printf("New max of %d found with n^2+%dn+%d\n",maxLength,maxA,maxB);
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}
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n=0;
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}
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}
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printf("\n\nProduct of maxes (%d*%d)=%ld\n",maxA,maxB,(long)maxA*maxB);
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return 0;
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}
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