85. Maximal Rectangle
Hard
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Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.
Example:
Input: [ ["1","0","1","0","0"], ["1","0","1","1","1"], ["1","1","1","1","1"], ["1","0","0","1","0"] ] Output: 6
IDEA:
https://www.twblogs.net/a/5bc0fa7d2b717711c9241544/zh-cn
The concept of monotone stack(单调栈) was introduced
ONE IMPORTANT THING:
dp[i][j] means the number of "1" in i rows before j columns.
dp[1][2]代表在第一行中的第二列之前1的个数。
#include#include #include<string> #include #include<set> #include
python version:
1.python version why don't duplicate the C++'s thought,this
method looks more complex.
2.this version complex to understand but I add some print point help
understand now paste method
class Solution(object): def maximalRectangle(self, matrix): """ :type matrix: List[List[str]] :rtype: int """ if not matrix or not matrix[0]: return 0 M, N = len(matrix), len(matrix[0]) height = [0] * N res = 0 for row in matrix: for i in range(N): if row[i] == '0': height[i] = 0 else: height[i] += 1 print("height1") print(height) res = max(res, self.maxRectangleArea(height)) return res def maxRectangleArea(self, height): if not height: return 0 print("height") print(height) res = 0 stack = list() print("stack0") print(stack) height.append(0) print("height2") print(height) for i in range(len(height)): cur = height[i] while stack and cur < height[stack[-1]]: print("stack") print(stack) w = height[stack.pop()] h = i if not stack else i - stack[-1] - 1 res = max(res, w * h) stack.append(i) return res solu = Solution() matirx=[ ["1","0","1","0","0"], ["1","0","1","1","1"], ["1","1","1","1","1"], ["1","0","0","1","0"] ] print(solu.maximalRectangle(matirx))