题目连接

 

Search a 2D Matrix II

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. 

For 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.

二分。。

class Solution {public:	bool searchMatrix(vector
     
      
       >& matrix, int target) {		if (matrix.empty() || matrix[0].empty()) return false;		n = matrix.size();		for (int i = 0; i < n; i++) {			It p = lower_bound(matrix[i].begin(), matrix[i].end(), target);			if (p != matrix[i].end() && *p == target) return true;		}		return false;	}private:	int n;	typedef vector
       
        ::iterator It;};