27 solved

Co-authored-by: sigonasr2 <sigonasr2@gmail.com>

archives/27/src/main.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include "utils.h"
+
+/*
+    Euler discovered the remarkable quadratic formula:
+
+
+    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.
+
+    The incredible formula  was discovered, which produces 80 primes for the consecutive values . The product of the coefficients, −79 and 1601, is −126479.
+
+    Considering quadratics of the form:
+
+    , where  and 
+
+    where  is the modulus/absolute value of 
+    e.g.  and 
+    Find the product of the coefficients,  and , for the quadratic expression that produces the maximum number of primes for consecutive values of , starting with .
+
+    https://projecteuler.net/problem=27
+*/
+
+int main(int argc,char**argv) {
+    FILE*f = fopen("archives/primegenerator/primes","r");
+    int startMarker=0;
+    while (fgetc(f)!='{') {
+        startMarker++;
+    }
+    int primes[2500];
+    char c;
+    int counter=0;
+    while (counter<2500) {
+        int digit=0;
+        while ((c=fgetc(f))!=',') {
+            digit*=10;
+            digit+=c-'0';
+        }
+        primes[counter++]=digit;
+    }
+    int n=0;
+
+    int maxLength=0;
+    int maxA=0;
+    int maxB=0;
+    
+    for (int a=-999;a<1000;a++) {
+        for (int b=-999;b<=1000;b++) {
+            for (int p=0;p<2500;p++) {
+                if (n*n+a*n+b==primes[p]) {
+                    n++;
+                    p=0;
+                }
+            }
+            if (n>maxLength) {
+                maxLength=n;
+                maxA=a;
+                maxB=b;
+                printf("New max of %d found with n^2+%dn+%d\n",maxLength,maxA,maxB);
+            }
+            n=0;
+        }
+    }
+    printf("\n\nProduct of maxes (%d*%d)=%ld\n",maxA,maxB,(long)maxA*maxB);
+
+    return 0;
+}

archives/27/src/utils.c

@@ -0,0 +1,173 @@
+#include "utils.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+struct String mult(struct String numb1, struct String numb2) {
+    struct String n1 = numb1;
+    struct String n2 = numb2;
+    byte carryover = 0;
+    if (numb2.length>numb1.length) {
+        n1=numb2;
+        n2=numb1;
+    }
+    int addends[n2.length][n1.length+1];
+    for (int i=0;i<n2.length;i++) {
+        for (int j=0;j<n1.length+1;j++) {
+            addends[i][j]=0;
+        }
+    }
+    for (int i=n2.length-1;i>=0;i--) {
+        carryover=0;
+        for (int j=n1.length-1;j>=0;j--) {
+            int mult = (n1.str[j]-'0')*(n2.str[i]-'0')+((carryover!=0)?carryover:0);
+            //printf("  %d/%d\n",mult,carryover);
+            carryover=0;
+            if (mult>=10) {
+                carryover=mult/10;
+                mult=mult%10;
+            }
+            addends[(n2.length-1)-i][j+1]=mult;
+        }
+        if (carryover>0) {
+            addends[(n2.length-1)-i][0]=carryover;
+        }
+    }
+    //printIntDoubleArr(n2.length,n1.length+1,addends);
+    struct String sum = {1,"0"};
+    for (int i=0;i<n2.length;i++) {
+        char val[n1.length+1+i];
+        for (int j=0;j<n1.length+1+i;j++) {
+            val[j]='0';
+        }
+        for (int j=0;j<n1.length+1;j++) {
+            val[j]=addends[i][j]+'0';
+        }
+        sum=add((struct String){n1.length+1+i,val},sum);
+        //printf("%s\n",sum.str);
+    }
+    if (sum.str[0]=='0') {
+        char*newStr=malloc(sum.length-1);
+        for (int i=1;i<sum.length;i++) {
+            newStr[i-1]=sum.str[i];
+        }
+        free(sum.str);
+        sum=(struct String){sum.length-1,newStr};
+    }
+    //printf("%s",sum.str);
+    return sum;
+}
+
+struct String add(struct String numb1, struct String numb2){
+    //printf("%s %s\n",numb1.str,numb2.str);
+    byte carryover=0;
+    int digitCount=0;
+    char*str = malloc(1);
+    //str[0]='\0';
+    if (numb1.length>=numb2.length) {
+        for (int offset=0;offset<numb1.length;offset++) {
+            str = realloc(str,++digitCount);
+            //printf("Digit count is now %d\n",digitCount);
+            if (numb2.length>offset) {
+                //printf("%c %c\n",numb1.str[numb1.length-offset-1],numb2.str[numb2.length-offset-1]);
+                int sum=((numb1.str[numb1.length-offset-1]-'0')+(numb2.str[numb2.length-offset-1]-'0'))+((carryover>0)?carryover--:0);
+                if (sum>=10) {
+                    carryover=1;
+                    sum-=10;
+                }
+                str[offset]=sum+'0';
+            } else {
+                str[offset]=numb1.str[numb1.length-offset-1]+((carryover>0)?carryover--:0);
+            }
+            //str[offset+1]='\0';
+        }
+    } else {
+        for (int offset=0;offset<numb2.length;offset++) {
+            str = realloc(str,++digitCount);
+            //printf("Digit count is now %d\n",digitCount);
+            if (numb1.length>offset) {
+                //printf("%c %c\n",numb1.str[numb1.length-offset-1],numb2.str[numb2.length-offset-1]);
+                int sum=((numb1.str[numb1.length-offset-1]-'0')+(numb2.str[numb2.length-offset-1]-'0'))+((carryover>0)?carryover--:0);
+                if (sum>=10) {
+                    carryover=1;
+                    sum-=10;
+                }
+                str[offset]=sum+'0';
+            } else {
+                str[offset]=numb2.str[numb2.length-offset-1]+((carryover>0)?carryover--:0);
+            }
+            //str[offset+1]='\0';
+        }
+    }
+    if (carryover>0) {
+        str = realloc(str,++digitCount);
+        str[digitCount-1]='1';
+        //str[digitCount]='\0';
+    }
+    for (int i=0;i<digitCount/2;i++) {
+        char c = str[i];
+        char c2 = str[digitCount-i-1];
+        str[digitCount-i-1]=c;
+        str[i]=c2;
+    }
+    str = realloc(str,digitCount+1);
+    str[digitCount]='\0';
+    struct String newStr = {digitCount,str};
+    return newStr;
+}
+
+void printLongDoubleArr(int a,int b,long doubleArr[a][b]) {
+    for (int i=0;i<a;i++) {
+        for (int j=0;j<b;j++) {
+            printf("%ld\t",doubleArr[i][j]);
+        }
+        printf("\n");
+    }
+}
+
+void printIntDoubleArr(int a,int b,int doubleArr[a][b]) {
+    for (int i=0;i<a;i++) {
+        for (int j=0;j<b;j++) {
+            printf("%d\t",doubleArr[i][j]);
+        }
+        printf("\n");
+    }
+}
+
+struct String createBigNumber(char*numb) {
+    int marker=0;
+    while (numb[marker++]!='\0');
+    return (struct String){marker-1,numb};
+}
+
+int*getFactors(int numb) {
+    int*factorList=malloc(sizeof(int)*1);
+    int factorListSize=2;
+    factorList[0]=1;
+    factorList[1]=numb;
+    int max=numb;
+    for (int i=2;i<max;i++) {
+        if (numb%i==0) {
+            factorList=realloc(factorList,sizeof(int)*++factorListSize);
+            factorList[factorListSize-1]=i;
+            if (numb/i!=i) {
+                factorList=realloc(factorList,sizeof(int)*++factorListSize);
+                factorList[factorListSize-1]=numb/i;
+                max=numb/i;
+            }
+        }
+    }
+    factorList=realloc(factorList,sizeof(int)*++factorListSize);
+    factorList[factorListSize-1]=0;
+    return factorList;
+}
+
+boolean isFactor(int*factorList,int numb) {
+    int counter=0;
+    while (factorList[counter]!=0) {
+        if (numb==factorList[counter]) {
+            return true;
+        }
+        counter++;
+    }
+    return false;
+}

archives/27/src/utils.h

@@ -0,0 +1,16 @@
+#define true 1
+#define false 0
+#define boolean char
+#define byte char
+struct String{
+    int length;
+    char*str;
+};
+struct String add(struct String numb1, struct String numb2);
+struct String mult(struct String numb1, struct String numb2);
+void printLongDoubleArr(int a,int b,long doubleArr[a][b]);
+void printIntDoubleArr(int a,int b,int doubleArr[a][b]);
+struct String createBigNumber(char*numb);
+#define BigNumber(X) createBigNumber(#X)
+boolean isFactor(int*factorList,int numb);
+int*getFactors(int numb);

src/main.c

@@ -26,15 +26,41 @@ int main(int argc,char**argv) {
     while (fgetc(f)!='{') {
         startMarker++;
     }
-    fseek(f,startMarker,SEEK_SET);
+    int primes[2500];
+    char c;
+    int counter=0;
+    while (counter<2500) {
+        int digit=0;
+        while ((c=fgetc(f))!=',') {
+            digit*=10;
+            digit+=c-'0';
+        }
+        primes[counter++]=digit;
+    }
     int n=0;
-    while (true) {
-        for (int a=1;a<1000;a++) {
-            for (int b=1;b<=1000;b++) {
 
+    int maxLength=0;
+    int maxA=0;
+    int maxB=0;
+    
+    for (int a=-999;a<1000;a++) {
+        for (int b=-999;b<=1000;b++) {
+            for (int p=0;p<2500;p++) {
+                if (n*n+a*n+b==primes[p]) {
+                    n++;
+                    p=0;
+                }
+            }
+            if (n>maxLength) {
+                maxLength=n;
+                maxA=a;
+                maxB=b;
+                printf("New max of %d found with n^2+%dn+%d\n",maxLength,maxA,maxB);
             }
+            n=0;
         }
     }
+    printf("\n\nProduct of maxes (%d*%d)=%ld\n",maxA,maxB,(long)maxA*maxB);
 
     return 0;
 }