[LeetCode]240.Search a 2D Matrix II

题目

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.

思路

杨氏矩阵

代码

/*---------------------------------------*   日期：2015-08-01*   作者：SJF0115*   题目: 240.Search a 2D Matrix II*   网址：https://leetcode.com/problems/search-a-2d-matrix-ii/*   结果：AC*   来源：LeetCode*   博客：-----------------------------------------*/#include <iostream>#include <vector>#include <stack>using namespace std;class Solution {public:    bool searchMatrix(vector<vector<int>>& matrix, int target) {        if(matrix.empty()){            return false;        }//if        int row = matrix.size();        int col = matrix[0].size();        int x = 0,y = col - 1;        // 杨氏矩阵解法从右上角元素开始        while(x < row && y >= 0){            if(matrix[x][y] == target){                return true;            }//if            else if(matrix[x][y] < target){                ++x;            }//else            else{                --y;            }        }//while        return false;    }};int main(){    Solution s;    int target = 20;    vector<vector<int> > 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}    };    bool result = s.searchMatrix(matrix,target);    // 输出    cout<<result<<endl;    return 0;}