LeetCode OJ:Search a 2D Matrix

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.

算法思想：二分

class Solution {public:    bool searchMatrix(vector<vector<int> > &matrix, int target) {        if(matrix.empty())return false;        int r=matrix.size();        int c=matrix[0].size();        int left=0,right=r*c-1;        while(left<=right){            int mid=(left+right)/2;            if(matrix[mid/c][mid%c]==target)return true;            if(matrix[mid/c][mid%c]<target)left=mid+1;            else right=mid-1;        }        return false;    }};