Annoying painting tool
| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 1736 | Accepted: 1165 |
Description
Maybe you wonder what an annoying painting tool is? First of all, the painting tool we speak of supports only black and white. Therefore, a picture consists of a rectangular area of pixels, which are either black or white. Second, there is only one operation
how to change the colour of pixels:
Select a rectangular area of r rows and c columns of pixels, which is completely inside the picture. As a result of the operation, each pixel inside the selected rectangle changes its colour (from black to white, or from
white to black).
Initially, all pixels are white. To create a picture, the operation described above can be applied several times. Can you paint a certain picture which you have in mind?
Input
The input contains several test cases. Each test case starts with one line containing four integers n, m, r and c. (1 ≤ r ≤ n ≤ 100, 1 ≤ c ≤ m ≤ 100), The following n lines
each describe one row of pixels of the painting you want to create. The ith line consists of m characters describing the desired pixel values of the ith row in the finished painting (‘0‘
indicates white, ‘1‘ indicates black).
The last test case is followed by a line containing four zeros.
Output
For each test case, print the minimum number of operations needed to create the painting, or -1 if it is impossible.
Sample Input
3 3 1 1 010 101 010 4 3 2 1 011 110 011 110 3 4 2 2 0110 0111 0000 0 0 0 0
Sample Output
4
6
-1
贪心思想，从上到下从左到右，如果这一块不是0，就一定要进行一个翻转操作，因为，这是个矩形，一定是在左上角翻转是最好的
因为这样，翻转有可能把接下来的方块一并翻转了，所以，只需要最后比较一个，是否达到要求即可！
// ConsoleApplication1.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"
#include "stdio.h"
#include "string.h"
#include "math.h"
#include <algorithm>
#include <vector>
#include <queue>
#include <iostream>
using namespace std;
#define N 105
#define SCANF scanf_s
int map[N][N];
void print(int n,int m){
for (int i = 0; i < n; i++){
for (int j = 0; j < m; j++){
cout<<map[i][j];
}
cout << endl;
}
}
int main()
{
int n, sum, m, r, c;
while (SCANF("%d%d%d%d", &n, &m, &r, &c) != EOF)
{
if (n == 0 && m == 0 && r == 0 && c == 0)
break;
getchar();
for (int i = 0; i < n; i++){
for (int j = 0; j < m; j++){
map[i][j] = getchar() == '0' ? 0 : 1;
}
getchar();
}
sum = 0;
for (int i = 0; i < n - r +1;i++)
for (int j = 0; j < m - c +1; j++){
if (map[i][j]){
for (int k = i; k < i + r;k++)
for (int s = j; s < j + c; s++){
map[k][s] = map[k][s] ? 0 : 1;
}
sum++;
}
}
//print(n, m);
bool flag = true;
for (int i = 0; i < n && flag;i++)
for (int j = 0; j < m&& flag;j++)
if (map[i][j]){
sum = -1;
flag = false;
}
cout << sum << endl;
}
return 0;
}