QuadTree 더블릿

#include <stdio.h>
#include <utility>
#include <queue>
#include <cmath>
#include <stack>
 
using namespace std;
queue<pair<pair<int, int>, int> > q;
stack<int> change;
stack<char> rst;
int arr[550][550] = { 0 };
 
int main() {
    int n;
    scanf("%d", &n);
 
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            scanf("%d", &arr[i][j]);
        }
    }
 
    pair<int, int> xy(1,1);    
    q.push(make_pair(xy,n));
    while (q.empty() == false) {
        int x = q.front().first.first;
        int y = q.front().first.second;
        int len = q.front().second;
        int flag = 0;
 
        q.pop();
 
        for (int i = y; i < y + len; i++) {
            for (int j = x; j < x + len; j++) {
                if (arr[y][x] != arr[i][j]) {
                    change.push(1);
                    // 분할, 하나씩
                    xy = make_pair(x, y);
                    q.push(make_pair(xy,len/2));
                    xy = make_pair(x+len/2, y);
                    q.push(make_pair(xy, len / 2));
                    xy = make_pair(x, y+len/2);
                    q.push(make_pair(xy, len / 2));
                    xy = make_pair(x+len/2, y+len/2);
                    q.push(make_pair(xy, len / 2));
                    // 탈출조건
                    flag = 1;
                    break;
                }
            }
            if (flag == 1)
                break;
        }
        // 모든 숫자가 일치할 경우, 분할 안함
        if (flag == 0) {
            change.push(0);
            change.push(arr[y][x]);            
        }        
    }
    int sixteen = 0, tmp=0;
    while (change.empty() == false) {     
        if (sixteen == 4) {
            if (tmp < 10)
                rst.push((char)('0' + tmp));                
            else
                rst.push((char)('A' + tmp - 10));
            sixteen = 0;
            tmp = 0;
        }
        if(change.top() == 1)
            tmp += (int) pow(2, sixteen);
        change.pop();
        sixteen++;
    }
    if (tmp != 0) {
        rst.push((char)('0' + tmp));        
    }
    // 결과값 rst에 넣어서 역순으로 출력하기
    while (rst.empty() == false) {
        printf("%c", rst.top());
        rst.pop();
    }
}