标签：msu ble amp red class type blank itil length
https://leetcode.com/problems/maximal-square/#/description
Given a 2D binary matrix filled with 0‘s and 1‘s, find the largest square containing only 1‘s and return its area.
For example, given the following matrix:
1 0 1 0 0 1 0 1 1 1 1 1 1 1 1 1 0 0 1 0
Return 4.
Sol 1:
Brute Force.
class Solution(object): def maximalSquare(self, matrix): """ :type matrix: List[List[str]] :rtype: int """ # brute force if len(matrix) <= 0 : return 0 rows = len(matrix) cols = len(matrix[0]) maxsqlen = 0 for i in range(rows): for j in range(cols): # initilize flag to be True if matrix[i][j] == ‘1‘: sqlen = 1 flag = True # border limits while sqlen + i < rows and sqlen + j < cols and flag: # advance square length downwords for k in range(j, sqlen + j + 1): if matrix[i+sqlen][k] == ‘0‘: flag = False break # advance square length to the right for k in range(i, sqlen + i + 1): if matrix[k][j+sqlen] == ‘0‘: flag = False break if flag: sqlen += 1 if maxsqlen < sqlen: maxsqlen = sqlen return maxsqlen * maxsqlen
Complexity Analysis
Sol 2:
DP.
（sth. wrong with initlization of DP...）
class Solution(object): def maximalSquare(self, matrix): """ :type matrix: List[List[str]] :rtype: int """ # DP # Time complexity : O(mn)O(mn). Single pass. # pace complexity : O(mn)O(mn). Another matrix of same size is used for dp. if len(matrix) <= 0 : return 0 rows = len(matrix) cols = len(matrix[0]) maxsqlen = 0 dp = [‘0‘] * (rows + 1) * (cols + 1) for i in range(1, rows+1): for j in range(1, cols+1): if matrix[i-1][j-1] == ‘1‘: dp[i][j] = min(dp[i][j-1], dp[i-1][j], dp[i-1][j-1]) + 1 maxsqlen = max(maxsqlen, dp[i][j]) return maxsqlen * maxsqlen
标签：msu ble amp red class type blank itil length
原文地址：http://www.cnblogs.com/prmlab/p/7220060.html
