Maximal Rectangle
问题描述
Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area.
For example, given the following matrix:
1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0
Return 6.
参考答案
class Solution {
public:
int maximalRectangle(vector<vector<char> > &matrix) {
if(matrix.empty()) return 0;
const int m = matrix.size();
const int n = matrix[0].size();
int left[n], right[n], height[n];
fill_n(left,n,0); fill_n(right,n,n); fill_n(height,n,0);
int maxA = 0;
for(int i=0; i<m; i++) {
int cur_left=0, cur_right=n;
for(int j=0; j<n; j++) { // compute height (can do this from either side)
if(matrix[i][j]=='1') height[j]++;
else height[j]=0;
}
for(int j=0; j<n; j++) { // compute left (from left to right)
if(matrix[i][j]=='1') left[j]=max(left[j],cur_left);
else {left[j]=0; cur_left=j+1;}
}
// compute right (from right to left)
for(int j=n-1; j>=0; j--) {
if(matrix[i][j]=='1') right[j]=min(right[j],cur_right);
else {right[j]=n; cur_right=j;}
}
// compute the area of rectangle (can do this from either side)
for(int j=0; j<n; j++)
maxA = max(maxA,(right[j]-left[j])*height[j]);
}
return maxA;
}
};