LeetCode 85. Maximal Rectangle
1 class Solution { 2 public: 3 int maximalRectangle(vector<vector<char>>& matrix) { 4 /** largest rectangle based solution **/ 5 if(matrix.size()<=0 || matrix[0].size()<=0) 6 return 0; 7 int m=matrix.size(); 8 int n=matrix[0].size()+1; 9 int h=0, w=0, result=0; 10 vector<int> height(n, 0); 11 for(int i=0; i<m; i++){ 12 stack<int> s; 13 for(int j=0; j<n; j++){ 14 /** update the current row ended height array **/ 15 if(j<n-1){ 16 if(matrix[i][j]=='1') height[j]+=1; 17 else height[j]=0; 18 } 19 /** use the histogram-max-rectangle-module **/ 20 while(!s.empty() && height[s.top()]>=height[j]){ 21 h=height[s.top()]; 22 s.pop(); 23 w=s.empty() ? j:j-s.top()-1; 24 if(h*w>result) result=h*w; 25 } 26 s.push(j); 27 } 28 } 29 return result; 30 } 31 };
1 class Solution { 2 public: 3 int maximalRectangle(vector<vector<char>>& matrix) { 4 if(matrix.empty()) return 0; 5 const int m=matrix.size(); 6 const int n=matrix[0].size(); 7 vector<int> left(n,0), right(n,n), height(n,0); 8 int result=0; 9 for(int i=0; i<m; i++){ 10 int cur_left=0, cur_right=n; 11 for(int j=0; j<n; j++){ 12 if(matrix[i][j]=='1') height[j]++; 13 else height[j]=0; 14 } 15 for(int j=0; j<n; j++){ 16 if(matrix[i][j]=='1') left[j]=max(left[j], cur_left); 17 else { left[j]=0; cur_left=j+1; } 18 } 19 for(int j=n-1; j>=0; j--){ 20 if(matrix[i][j]=='1') right[j]=min(right[j], cur_right); 21 else { right[j]=n; cur_right=j; } 22 } 23 for(int j=0; j<n; j++){ 24 result=max(result, (right[j]-left[j])*height[j]); 25 } 26 } 27 return result; 28 } 29 };
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