Submission #235064

#	Time	Username	Problem	Language	Result	Execution time	Memory
235064		UserIsUndefined	Rectangles (IOI19_rect)	C++14	0 / 100	5084 ms	59488 KiB

rect

#include "rect.h"
#include <bits/stdc++.h>



int presum[3000][3000];


using namespace std;

long long count_rectangles(std::vector<std::vector<int> > a) {
    int n = a.size();
    int m = a[0].size();
    long long ans = 0;

    for (int i = 0 ; i < n ; i++){
        for (int j = 0 ; j < m ; j++){
            if (j == 0)presum[i][j] = a[i][j];
            else presum[i][j] = presum[i][j-1] + a[i][j];
        }
    }

    for (int j = 0 ; j < m ; j++){
        for (int i = 1 ; i < n ; i++){
            presum[i][j] = presum[i - 1][j] + presum[i][j];
        }
    }


    vector<pair<int,int>> zeros;


    for (int i = 1 ; i < n - 1 ; i++){
        for (int j = 1 ; j < m - 1 ; j++){
            if (a[i][j] == 0)zeros.push_back({i,j});
        }
    }



    for (int i = 0 ; i < zeros.size() ; i++){
        for (int j = 0 ; j < zeros.size() ; j++){
            int x0,y0,x1,y1;
            x0 = zeros[i].first; x1 = zeros[j].first; y0 = zeros[i].second ; y1 = zeros[j].second;

            if (x1 < x0 || y1 < y0)continue;

            int big0, small0, rec01, rec02, sum0;

            big0 = presum[x1][y1];
            small0 = presum[x0 - 1][y0 - 1];
            rec01 = presum[x1][y0 - 1];
            rec02 = presum[x0 - 1][y1];

            sum0 = big0 - rec01 - rec02 + small0;

            if (sum0 != 0)continue;

            big0 = presum[x1 + 1][y1 + 1];
            small0 = (x0 == 1 || y0 == 1 ? 0 : presum[x0 - 2][y0 - 2]);
            rec01 = (y0 == 1 ? 0 : presum[x1 + 1][y0 - 2]);
            rec02 = (x0 == 1 ? 0 : presum[x0 - 2][y1 + 1]);

            sum0 = big0 - rec01 - rec02 + small0;

            int atfirst = sum0;

            sum0-= (a[x1 + 1][y1 + 1] == 1 ? 1 : 0);
            sum0-= (a[x0 - 1][y0 - 1] == 1 ? 1 : 0);
            sum0-= (a[x1 + 1][y0 - 1] == 1? 1 : 0);
            sum0-= (a[x0 - 1][y1 + 1] == 1? 1 : 0);

            int should = x1 - x0 + 1;
            should+= (y1 - y0 + 1);
            should*= 2;

            if (sum0 == should){
                ans++;
//                cout << "from (" << x0 << "," << y0 << ") to (" << x1 << "," << y1 << endl;
//                cout << "should =" << should << endl;
//                cout << "at first  = " << atfirst << endl;


            }

        }
    }

    return ans;

}

Compilation message (stderr)

rect.cpp: In function 'long long int count_rectangles(std::vector<std::vector<int> >)':
rect.cpp:41:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0 ; i < zeros.size() ; i++){
                      ~~^~~~~~~~~~~~~~
rect.cpp:42:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0 ; j < zeros.size() ; j++){
                          ~~^~~~~~~~~~~~~~
rect.cpp:66:17: warning: unused variable 'atfirst' [-Wunused-variable]
             int atfirst = sum0;
                 ^~~~~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 7
• Subtask 3: 0 / 12
• Subtask 4: 0 / 22
• Subtask 5: 0 / 10
• Subtask 6: 0 / 13
• Subtask 7: 0 / 28