2^100000

bigint.c

#include <stdio.h>
#include <stdlib.h>

#define BASE 10000

struct number {
    int n;
    int *a;
};
typedef struct number *N;

N allocate_number(int n) {
    N v;
    v = (N)malloc(sizeof(struct number));
    v->n = n;
    v->a = (int *)calloc(n, sizeof(int));
    return v;
}

void free_number(N a) {
    free(a->a);
    free(a);
}

N make_number(int i) {
    N v;
    v = allocate_number(1);
    v->a[0] = i;
    return v;
}

N multiply_number(N a, N b) {
    int i, j, k;
    int da, db, carry;
    N c = allocate_number(a->n + b->n);    
    for (i = 0; i < a->n; i++) {
        da = a->a[i];
        carry = 0;
        for (j = 0, k = i; j < b->n; j++, k++) {
            db = b->a[j];
            carry += c->a[k] + da * db;
            c->a[k] = carry % BASE;
            carry /= BASE;
        }
        if (carry)
            c->a[k] += carry;
    }
    return c;
}

void print_number(N a) {
    int i, d;
    int first = 1;
    for (i = a->n-1; i > -1; i--) {
        d = a->a[i];
        if (d) {
            printf(first ? "%d" : "%04d", d);
            first = 0;
        }
    }
    printf("\n");
}

N tenth_power_of_number(N a) {
    N a2, a4, a5, a10;
    a2 = multiply_number(a, a);
    a4 = multiply_number(a2, a2);
    a5 = multiply_number(a4, a);
    a10 = multiply_number(a5, a5);
    free_number(a2);
    free_number(a4);
    free_number(a5);
    return a10;
}

int main() {
    int i;
    N a, b;
    a = make_number(2);
    for (i = 0; i < 5; i++) {
        b = tenth_power_of_number(a);
        free_number(a);
        a = b;
    }
    print_number(a);
    return 0;
}