[leetcode 240]Search a 2D Matrix II

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<vector<int>>& 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<rows&&x>=0)
    {
        if(matrix[y][x]==target)
            return true;
        else if(matrix[y][x]>target)
            --x;
        else
            ++y;
    }
    return false;
    }
};

其它Leetcode题目AC代码：https://github.com/PoughER/leetcode