LeetCode：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.

方法一：

// Source : https://oj.leetcode.com/problems/search-a-2d-matrix/// Author : Chao Zeng// Date   : 2015-1-27class Solution {public:    //杨氏矩阵里面查找某个数，最佳时间复杂度O(m+n)    bool searchMatrix(vector<vector<int> > &matrix, int target) {        int row = matrix.size();        int column = matrix[0].size();        int rows = 0;        int columns = column;        while (rows < row && columns > 0){            if (matrix[rows][columns-1] == target)                return true;            else if (matrix[rows][columns-1] > target)                columns--;            else                rows++;        }        return false;    }};

方法二：

// Source : https://oj.leetcode.com/problems/search-a-2d-matrix/// Author : Chao Zeng// Date   : 2015-1-27class Solution {public:    //循环遍历O(n*n)    bool searchMatrix(vector<vector<int> > &matrix, int target) {        int row = matrix.size();        int column = matrix[0].size();        for (int i = 0; i < row ; i++){            for (int j = 0; j < column; j++){                if (target == matrix[i][j])                    return true;            }        }        return false;    }};