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.

两边逼近

class Solution {public:    bool searchMatrix(vector<vector<int> > &matrix, int target) {        int i = 0, j = matrix[0].size()-1;        while(i <  matrix.size() && j >= 0){          if(matrix[i][j] == target)            return true;          else if(matrix[i][j] < target)            i++;          else            j--;        }        return false;    }};