Create 0221-maximal-square.cpp

Author: Abe0770

cpp/0221-maximal-square.cpp

@@ -0,0 +1,33 @@
+/*
+  Given an m x n binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.
+
+  Ex. Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
+      Output: 4
+
+  Time  : O(m*n)
+  Space : O(m*n)
+*/
+
+class Solution {
+public:
+    int maximalSquare(vector<vector<char>>& matrix) {
+        int rows = matrix.size(), cols = matrix[0].size();
+
+        vector<vector<int>> dp (rows+1, vector<int>(cols+1, 0));
+        int maxi = 0;
+        for(int i = rows-1 ; i >= 0; --i) {
+            for(int j = cols-1 ; j >=0 ; --j) {
+                if(matrix[i][j] == '1') {
+                    int right = dp[i][j+1], dia = dp[i+1][j+1], bottom = dp[i+1][j];
+                    
+                    dp[i][j] = 1 + min(right, min(dia, bottom));
+                    maxi = max(maxi, dp[i][j]);
+                }
+                else {
+                    dp[i][j] = 0;
+                }
+            }
+        }
+        return maxi*maxi;
+    }
+};