240. Search a 2D Matrix II

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.

 

有序矩阵查找

 

C++:

 1 class Solution {
 2 public:
 3     bool searchMatrix(vector<vector<int>>& matrix, int target) {
 4         int n = matrix.size() ;
 5         if (n == 0)
 6             return false ;
 7         int m = matrix[0].size() ;
 8         int i = 0 ;
 9         int j = m-1 ;
10         while(i < n && j >= 0){
11             if (matrix[i][j] == target){
12                 return true ;
13             }else if (matrix[i][j] > target){
14                 j-- ;
15             }else{
16                 i++ ;
17             }
18         }
19         return false ;
20     }
21 };

 

posted @ 2019-01-16 11:07  __Meng  阅读(117)  评论(0)  编辑  收藏  举报