20 complete!

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

archives/20/src/main.c

@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include "utils.h"
+#include <stdlib.h>
+
+/*
+    n! means n × (n − 1) × ... × 3 × 2 × 1
+
+    For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
+    and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
+
+    Find the sum of the digits in the number 100!
+
+
+    https://projecteuler.net/problem=20
+*/
+
+
+int digitCount(int numb) {
+    int digitCount=1;
+    while (numb>=10) {
+        numb/=10;
+        digitCount++;
+    }
+    return digitCount;
+}
+
+char*numberToString(int numb) {
+    char*num=malloc(digitCount(numb));
+    int counter=digitCount(numb)-1;
+    while (numb!=0) {
+        num[counter--]=(numb%10)+'0';
+        numb/=10;
+    }
+    return num;
+}
+
+int main(int argc,char**argv) {
+    struct String factorialSum = {1,"1"};
+    int counter=2;
+    while (counter<=100) {
+        factorialSum=mult(factorialSum,(struct String){digitCount(counter),numberToString(counter)});
+        printf("%s\n",factorialSum.str);
+        counter++;
+    }
+
+    printf("%s",factorialSum.str);
+    int digitSum=0;
+    for (int i=0;i<factorialSum.length;i++) {
+        digitSum+=factorialSum.str[i]-'0';
+    }
+    printf("\nThe sum of the digits are %d",digitSum);
+
+    return 0;
+}

archives/20/src/utils.c

@@ -0,0 +1,128 @@
+#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(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);
+            }
+        }
+    } 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);
+            }
+        }
+    }
+    if (carryover>0) {
+        str = realloc(str,++digitCount);
+        str[digitCount-1]='1';
+    }
+    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;
+    }
+    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");
+    }
+}

archives/20/src/utils.h

@@ -0,0 +1,12 @@
+#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]);

src/main.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include "utils.h"
+#include <stdlib.h>
 
 /*
     n! means n × (n − 1) × ... × 3 × 2 × 1
@@ -12,13 +13,42 @@
 
     https://projecteuler.net/problem=20
 */
+
+
+int digitCount(int numb) {
+    int digitCount=1;
+    while (numb>=10) {
+        numb/=10;
+        digitCount++;
+    }
+    return digitCount;
+}
+
+char*numberToString(int numb) {
+    char*num=malloc(digitCount(numb));
+    int counter=digitCount(numb)-1;
+    while (numb!=0) {
+        num[counter--]=(numb%10)+'0';
+        numb/=10;
+    }
+    return num;
+}
+
 int main(int argc,char**argv) {
-    struct String factorialSum = {1,"0"};
+    struct String factorialSum = {1,"1"};
-    int counter=1;
+    int counter=2;
-    printf("%s",mult((struct String){14,"85018361849301"},(struct String){7,"1849204"}).str);
     while (counter<=100) {
+        factorialSum=mult(factorialSum,(struct String){digitCount(counter),numberToString(counter)});
+        printf("%s\n",factorialSum.str);
         counter++;
     }
 
+    printf("%s",factorialSum.str);
+    int digitSum=0;
+    for (int i=0;i<factorialSum.length;i++) {
+        digitSum+=factorialSum.str[i]-'0';
+    }
+    printf("\nThe sum of the digits are %d",digitSum);
+
     return 0;
 }

src/utils.c

@@ -20,7 +20,7 @@ struct String mult(struct String numb1, struct String numb2) {
         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);
+            //printf("  %d/%d\n",mult,carryover);
             carryover=0;
             if (mult>=10) {
                 carryover=mult/10;
@@ -32,7 +32,7 @@ struct String mult(struct String numb1, struct String numb2) {
             addends[(n2.length-1)-i][0]=carryover;
         }
     }
-    printIntDoubleArr(n2.length,n1.length+1,addends);
+    //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];
@@ -45,6 +45,14 @@ struct String mult(struct String numb1, struct String numb2) {
         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;
 }