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Author: assassint2017

Maximal Square/Maximal_Square.cpp

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+// 动态规划
+
+// Runtime: 16 ms, faster than 97.02% of C++ online submissions for Maximal Square.
+// Memory Usage: 10.6 MB, less than 86.19% of C++ online submissions for Maximal Square.
+
+class Solution 
+{
+public:
+    int maximalSquare(vector<vector<char>>& matrix) 
+    {
+        // 边界条件处理
+        int rows = matrix.size();
+        if (rows == 0) return 0;
+
+        int cols = matrix[0].size();
+        if (cols == 0) return 0;
+
+        int maxArea = 0;
+        vector<int> left(cols, -1);
+        vector<int> right(cols, cols);
+        vector<int> height(cols, 0);
+
+        for (int i = 0; i < rows; ++i)
+        {
+            int curLeft = 0, curRight = cols - 1;
+
+            for (int j = 0; j < cols; ++j)
+            {
+                if (matrix[i][j] == '1')
+                {
+                    left[j] = max(left[j], curLeft);
+                    ++height[j];
+                }
+                else
+                {
+                    height[j] = 0;
+                    curLeft = j + 1;
+                    left[j] = -1;
+                }
+            }
+
+            for (int j = cols - 1; j >= 0; --j)
+            {
+                if (matrix[i][j] == '1')
+                {
+                    right[j] = min(right[j], curRight);
+
+                    int h = height[j];
+                    int w = right[j] - left[j] + 1;
+                    maxArea = max(maxArea, min(w, h) * min(w, h));
+                }
+                else
+                {
+                    curRight = j - 1;
+                    right[j] = cols;
+                }
+            }   
+        }
+        return maxArea;
+    }
+};