Update and rename maximalRectangle.cpp to maximal-rectangle.cpp

Author: kamyu104

C++/maximal-rectangle.cpp

@@ -0,0 +1,46 @@
+// Time:  O(m * n)
+// Space: O(n)
+
+class Solution {
+public:
+    int maximalRectangle(vector<vector<char> > &matrix) {
+        if(matrix.empty())
+            return 0;
+
+        const int m = matrix.size();
+        const int n = matrix.front().size();
+
+        int ans = 0;
+
+        vector<int> H(n, 0);  // height of all ones rectangle include matrix[i][j]
+        vector<int> L(n, 0);  // left closed bound of all ones rectangle include matrix[i][j]
+        vector<int> R(n, n);  // right open bound of all onces rectangle include matrix[i][j]
+
+        for(int i = 0; i < m; ++i) {
+            int left = 0, right = n;
+            for(int j = 0; j < n; ++j) {
+                if(matrix[i][j] == '1') {
+                    ++H[j];  // update height
+                    L[j] = max(L[j], left); // update left bound
+                }
+                else {
+                    left = j + 1;
+                    H[j] = L[j] = 0;
+                    R[j] = n;
+                }
+            }
+
+            for(int j = n - 1; j >= 0; --j) {
+                if(matrix[i][j] == '1') {
+                    R[j] = min(R[j], right);  // update right bound
+                    ans = max(ans, H[j] * (R[j] - L[j]));
+                }
+                else {
+                    right = j;
+                }
+            }
+        }
+
+        return ans;
+    }
+};