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.

解析：

二分查找，中间变换一下坐标

代码：

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