1023 Have Fun with Numbers (20)

#include<stdio.h>
#include<string.h>
struct bign {
    int d[21], len;
    bign() {
        memset(d, 0, sizeof(d));
        len = 0;
    }
};
bign change(char str[]) {
    bign a;
    a.len = strlen(str);
    for (int i = 0; i < a.len; i++) {
        a.d[i] = str[a.len - i - 1] - '0';
    }
    return a;
}

bign multi(bign a, int b) {
    bign c;
    int carry = 0;
    for (int i = 0; i < a.len; i++) {
        int temp = a.d[i] * b + carry;
        c.d[c.len++] = temp % 10;
        carry = temp / 10;
     }
    while (carry != 0) {   //**
        c.d[c.len++] = carry % 10;
        carry /= 10;
    }
    return c;
}
bool Judge(bign a, bign c) {
    if (a.len != c.len) return false;
    int count[10] = { 0 };
    for (int i = 0; i < a.len; i++) {
        count[a.d[i]]++;
        count[c.d[i]]--;
    }
    for (int i = 0; i < 10; i++) {
        if (count[i] != 0) return false;
    }
    return true;
}


int main() {
    char str[21];
    scanf("%s", str);
    bign a = change(str);
    bign c = multi(a, 2);
    if (Judge(a, c) == true) printf("Yes\n");
    else printf("No\n");
    for (int i = c.len - 1; i >= 0; i--) {
        printf("%d", c.d[i]);
    }
    return 0;
}