PAT 1023 Have Fun with Numbers

#include <cstdio>
#include <cstdlib>
#include <vector>

using namespace std;

bool double_num(vector<char> &num) {
int carry = 0;
int i = num.size() - 1;
while (i>=0) {
int d = num[i] * 2 + carry;
carry = d / 10;
num[i]= d % 10;
i--;
}
return carry < 1;
}

void stat_count(vector<char>& num, int* cnt) {
for (int i=num.size() - 1; i>=0; i--) {
cnt[num[i]]++;
}
}

bool is_same_digits(vector<char>& num, int* cnt) {
int cur_cnt[10] = {0};

stat_count(num, cur_cnt);

for (int i=0; i<10; i++) {
if (cnt[i] != cur_cnt[i]) return false;
}
return true;
}

void print(vector<char> &num) {
int len = num.size();
for (int i=0; i<len; i++) {
printf("%d", num[i]);
}
printf("\n");
}

int main() {
const int MAX_DIGITS = 20;

vector<char> num;

char buf[MAX_DIGITS + 1];

int count[10] = {0};

scanf("%s", buf);

for (int i=0; buf[i] != '\0'; i++) {
if (num.empty() && buf[i] == '0') continue; // skip leading zeros
num.push_back(buf[i] - '0');
}
if (num.empty()) num.push_back(0);

// stat original number digit count
stat_count(num, count);

bool found = false;
bool no_carry = double_num(num);

bool is_same = is_same_digits(num, count);
if (is_same) {
printf("Yes\n");
} else {
printf("No\n");
}
if (!no_carry) printf("1");
print(num);
return 0;
}