LeetCode240. Search a 2D Matrix II
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Difficulty:medium
More:【目录】LeetCode Java实现
Description
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
- Integers in each row are sorted in ascending from left to right.
- Integers in each column are sorted in ascending from top to bottom.
Example:
Consider the following matrix:
[ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 22], [10, 13, 14, 17, 24], [18, 21, 23, 26, 30] ]
Given target = 5
, return true
.
Given target = 20
, return false
.
Intuition
refer to 二维数组中的查找
Solution
public boolean searchMatrix(int[][] matrix, int target) { if(matrix==null || matrix.length<=0 || matrix[0].length<=0) return false; int row=0; int col=matrix[0].length-1; while(row<matrix.length && col>=0){ if(matrix[row][col]==target) return true; else if(matrix[row][col]>target) col--; else if(matrix[row][col]<target) row++; } return false; }
Complexity
Time complexity : O(m+n)
Space complexity : O(1)
What I\'ve learned
1. Ought to have a good command of the thought in this problem.
More:【目录】LeetCode Java实现
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