c program to find power of a large number | CTechnotips


C code for power of very big numbers:  

#include<stdio.h>
#include<string.h>

#define MAX 10000

char * multiply(char [],char[]);

int main(){
    char a[MAX];
    char *c;
    int i,n;
    printf("Enter the base number: ");
    scanf("%s",a);
    printf("Enter the power: ");
    scanf("%d",&n);
    printf("Power of the %s^%d: ",a,n);
    c = multiply(a,"1");
    for(i=0;i<n-1;i++)
         c = multiply(a,c);
    while(*c)
    if(*c =='0')
         c++;
    else
         break;
    printf("%s",c);
    return 0;
}

char * multiply(char num1[],char num2[]){
    static char mul[MAX];
    char a[MAX];
    char b[MAX];
    char c[MAX];
    char temp[MAX];
    int la,lb;
    int i=0,j,k=0,x=0,y;
    long int r=0;
    long sum = 0;
   
    while(num1[i]){
         a[i] = num1[i];
         i++;
    }
    a[i]= '\0';
    i=0;
    while(num2[i]){
         b[i] = num2[i];
         i++;
    }
    b[i]= '\0';
    la=strlen(a)-1;
        lb=strlen(b)-1;
  
        for(i=0;i<=la;i++){
                a[i] = a[i] - 48;
        }
        for(i=0;i<=lb;i++){
                b[i] = b[i] - 48;
        }
    for(i=lb;i>=0;i--){
         r=0;
         for(j=la;j>=0;j--){
             temp[k++] = (b[i]*a[j] + r)%10;
             r = (b[i]*a[j]+r)/10;
         }
         temp[k++] = r;
         x++;
         for(y = 0;y<x;y++){
             temp[k++] = 0;
         }
    }
  
    k=0;
    r=0;
    for(i=0;i<la+lb+2;i++){
         sum =0;
         y=0;
         for(j=1;j<=lb+1;j++){
             if(i <= la+j){
                 sum = sum + temp[y+i];
             }
             y += j + la + 1;
         }
         c[k++] = (sum+r) %10;
         r = (sum+r)/10;
    }
    c[k] = r;
    j=0;
    for(i=k-1;i>=0;i--){
         mul[j++]=c[i] + 48;
    }
    mul[j]='\0';
    return mul;
}

Sample output:

Enter the base number: 5
Enter the power: 100
Power of the 5^100: 78886090522101180541172856528278622
96732064351090230047702789306640625

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