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.

矩阵排列规则。同一行从左往右递增，同一列从上往下递增，从右上角的数字下手

AC代码

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

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