start of 27

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

src/main.c

@@ -1,211 +1,40 @@
 #include <stdio.h>
 #include "utils.h"
-#include <stdlib.h>
 
 /*
-    A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:
+    Euler discovered the remarkable quadratic formula:
 
-    1/2	= 	0.5
-    1/3	= 	0.(3)
-    1/4	= 	0.25
-    1/5	= 	0.2
-    1/6	= 	0.1(6)
-    1/7	= 	0.(142857)
-    1/8	= 	0.125
-    1/9	= 	0.(1)
-    1/10	= 	0.1
-    Where 0.1(6) means 0.166666..., and has a 1-digit recurring cycle. It can be seen that 1/7 has a 6-digit recurring cycle.
 
-    Find the value of d < 1000 for which 1/d contains the longest recurring cycle in its decimal fraction part.
+    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.
 
-    https://projecteuler.net/problem=26
+    The incredible formula  was discovered, which produces 80 primes for the consecutive values . The product of the coefficients, −79 and 1601, is −126479.
-*/
 
-boolean isPrime(int*primeList,int primeListSize,int numb) {
+    Considering quadratics of the form:
-    for (int i=0;i<primeListSize;i++) {
-        if (numb==primeList[i]) {
-            return true;
-        }
-    }
-    return false;
-}
 
-int*getFactors(int numb) {
+    , where  and 
-    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) {
+    where  is the modulus/absolute value of 
-    int counter=0;
+    e.g.  and 
-    while (factorList[counter]!=0) {
+    Find the product of the coefficients,  and , for the quadratic expression that produces the maximum number of primes for consecutive values of , starting with .
-        if (numb==factorList[counter]) {
-            return true;
-        }
-        counter++;
-    }
-    return false;
-}
 
-const int TARGET_REPEATS_REQUIRED=100000;
+    https://projecteuler.net/problem=27
+*/
 
 int main(int argc,char**argv) {
-    int divider=0;
-    int divisor=2;
-    int sequence[TARGET_REPEATS_REQUIRED]; //Let's assume for the sake of sanity that 100000 repeating digits is enough. I sure hope so.
-    int sequenceLength=0;
-    int sequenceRepeat=0;
-    int sequenceMarker=-1;
-    int longestCycleLength=0;
-    int longestCycleDivisor=0;
-    int longestSequence[TARGET_REPEATS_REQUIRED/10];
-    int*primeList=malloc(sizeof(int)*0);
-    int primeListSize=0;
-
     FILE*f = fopen("archives/primegenerator/primes","r");
-    while (fgetc(f)!='{');
+    int startMarker=0;
-    while (true) {
+    while (fgetc(f)!='{') {
-        char c;
+        startMarker++;
-        int digit=0;
-        while ((c=fgetc(f))!=',') {
-            digit*=10;
-            digit+=c-'0';
-        }   
-        if (digit>=1000) {
-            break;
-        } else {
-            primeList=realloc(primeList,sizeof(int)*++primeListSize);
-            primeList[primeListSize-1]=digit;
-        }
     }
+    fseek(f,startMarker,SEEK_SET);
+    int n=0;
+    while (true) {
+        for (int a=1;a<1000;a++) {
+            for (int b=1;b<=1000;b++) {
 
-    while (divisor<1000) {
-        divider=10; //We always start with 10.
-        sequenceLength=0;
-        sequenceRepeat=0;
-        for (int i=0;i<sequenceLength;i++) {
-            sequence[i]=0;
-        }
-        sequenceMarker=-1;
-        while (sequenceLength<TARGET_REPEATS_REQUIRED) {
-            int result=divider/divisor;
-            //printf("%d/%d = %d\n",divider,divisor,result);
-            divider=divider%divisor;
-            sequence[sequenceLength++]=result;
-            divider*=10;
-            if (divider==0) {
-                //We're solved.
-                break;
             }
         }
-        /*printf("%d:",divisor);
-        for (int i=0;i<sequenceLength;i++) {
-            printf("%d",sequence[i]);
-        }
-        printf("\n");*/
-        //We need to look at all combinations of possible repeating sequences.
-        //Starting from iteration loop of length 1, and an offset incrementing by 1, see if anything remains the same.
-        //Then do this for iteration loop of length 2, offset incrementing by 1, etc.
-        //Find it repeating at least 20 times to assume it repeats infinitely.
-        boolean isP = isPrime(primeList,primeListSize,divisor);
-        int*factors = getFactors(divisor-1);
-        int counter=0;
-        /*if (isP) {
-            printf("Possible length factors of (%d-1):",divisor);
-            while (factors[counter]!=0) {
-                printf("%d,",factors[counter]);
-                counter++;
-            }
-            printf("\n");
-        }*/
-        boolean matched=false;
-        if (sequenceLength==TARGET_REPEATS_REQUIRED) {
-            for (int checkLength=0;checkLength<TARGET_REPEATS_REQUIRED/10;checkLength++) {
-                if (isP&&!isFactor(factors,checkLength+1)) {continue;}
-                for (int offset=0;offset<sequenceLength+1-checkLength;offset++) {
-                    int sequenceStore[checkLength+1];
-                    int requiredCheckAmt=TARGET_REPEATS_REQUIRED/10-2;
-                    for (int i=0;i<checkLength+1;i++) {
-                        sequenceStore[i]=sequence[i+offset];
-                        /*printf("%d:",divisor);
-                        for (int i=0;i<checkLength+1;i++) {
-                            printf("%d",sequenceStore[i]);
-                        }
-                        0010030090270812437311935807422266800401203610832497492477432296890672016048144433299899699097291875626880641925777331995987963891675025075225677031093279839518555667
-                        0010030090270812437311935807422266800401203610832497492477432296890672016048144433299899699097291875626880641925777331995987963891675025075225677031093279839518555667
-                        printf("\n");*/
-                    }
-                    //Now if this repeating sequence can be found requiredCheckAmt times, we're golden.
-                    boolean allMatching=true;
-                    int currentOffset=0;
-                    int found=0;
-                    while (requiredCheckAmt>0&&found<20) {
-                        for (int i=0;i<checkLength+1;i++) {
-                            //printf("  Compare %d to %d\n",sequence[offset+currentOffset+checkLength+1+i],sequenceStore[i]);
-                            if (sequence[offset+currentOffset+checkLength+1+i]!=sequenceStore[i]) {
-                                allMatching=false;
-                                goto check;
-                            }
-                        }
-                        requiredCheckAmt--;
-                        currentOffset+=checkLength+1;
-                        found++;
-                        //printf("Found a repeat.");
-                    }
-                    check:
-                    if (allMatching) {
-                        printf("Longest repeating sequence for %d is of length %d: ",divisor,checkLength+1);
-                        for (int i=0;i<checkLength+1;i++) {
-                            printf("%d",sequenceStore[i]);
-                        }
-                        printf("\n");
-                        if (longestCycleLength<checkLength+1) {
-                            longestCycleLength=checkLength+1;
-                            longestCycleDivisor=divisor;
-                            for (int i=0;i<longestCycleLength;i++) {
-                                longestSequence[i]=sequenceStore[i];
-                            }
-                        }
-                        matched=true;
-                        goto next;
-                    }
-                }
-            }
-        } else {
-            matched=true;
-            printf("Longest repeating sequence for %d is of length 0.\n",divisor);
-        }
-        next:
-        free(factors);
-        if (!matched) {
-            printf("Not enough data to calculate longest repeating sequence for %d!\nQuitting...\n",divisor);
-            return 1;
-        }
-        divisor++;
-    }
-
-    printf("\n\nThe largest repeating sequence length is from %d with %d in length.",longestCycleDivisor,longestCycleLength);
-    printf("\n\tSequence: ");
-    for (int i=0;i<longestCycleLength;i++) {
-        printf("%d",longestSequence[i]);
     }
-    printf("\n");
 
     return 0;
 }