(leetcode)Search a 2D Matrix

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 from left to right.
  • The first integer of each row is greater than the last integer of the previous row.

 

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

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

 

posted @ 2015-08-20 14:59  sunalive  Views(151)  Comments(0)    收藏  举报