Feb 1

Author: aliasvishnu

**85-MaximalRectangle.cpp

@@ -0,0 +1,63 @@
+class Solution {
+public:
+
+    int calculateMaxRectangle(vector<int> V){
+        stack<int> stk;
+
+        int len = V.size(), i = 0, answer = 0;
+
+        while(i < len){
+
+            if(stk.empty() || V[stk.top()] < V[i]){
+                stk.push(i++);
+            } else {
+                int ind = stk.top();
+                stk.pop();
+
+                 // compute height.
+                int candidate = V[ind] * ((stk.empty())? i: i - stk.top() - 1 );
+                answer = (candidate > answer)? candidate: answer;
+            }
+
+        }
+
+        while(!stk.empty()){
+            int ind = stk.top();
+            stk.pop();
+
+             // compute height.
+            int candidate = V[ind] * ((stk.empty())? i: i - stk.top() - 1 );
+            answer = (candidate > answer)? candidate: answer;
+        }
+
+        return answer;
+    }
+
+    int maximalRectangle(vector<vector<char>>& M) {
+        int rows = M.size();
+        if(rows == 0) return 0;
+        int cols = M[0].size();
+
+        vector<vector<int>> TC (rows, vector<int> (cols, 0));
+
+        int answer = 0;
+
+        for(int i = 0; i < cols; i++) TC[0][i] = M[0][i] == '1';
+
+        for(int i = 1; i < rows; i++){
+            for(int j = 0; j < cols; j++){
+                TC[i][j] = (M[i][j] == '1') ? TC[i-1][j] + 1: 0;
+            }
+        }
+
+
+        for(int i = 0; i < rows; i++){
+            int max_rectangle = calculateMaxRectangle(TC[i]);
+            if(max_rectangle > answer){
+                answer = max_rectangle;
+            }
+        }
+
+        return answer;
+    }
+};