Leetcode 85. Maximal Rectangle (Hard) (cpp)

Leetcode 85. Maximal Rectangle (Hard) (cpp)

Tag: Array, Hash Table, Stack, Dynamic Programming

Difficulty: Hard

/*85. Maximal Rectangle (Hard)Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.For example, given the following matrix:1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0Return 6.*/class Solution {public:int maximalRectangle(vector<vector<char>>& matrix) {if (matrix.empty()) {return 0;}int maxRec = 0;vector<int> height(matrix[0].size());for (int i = 0; i < matrix.size(); i++) {for (int j = 0; j < matrix[0].size(); j++) {height[j] = matrix[i][j] == '0' ? 0 : height[j] + 1;}maxRec = max(maxRec, largestRectangleArea(height));}return maxRec;}private:int largestRectangleArea(const vector<int>& heights) {stack<int> s;int maxSize = 0;for (int i = 0; i <= heights.size(); i++) {int cur = i == heights.size() ? 0 : heights[i];while (!s.empty() && heights[s.top()] >= cur) {int height = heights[s.top()];s.pop();int left = s.empty() ? 0 : s.top() + 1;maxSize = max(maxSize, (i - left) * height);}s.push(i);}return maxSize;}};