首先题目如下所示： 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.
解题思路：从右上角开始往左下角找寻答案，如果大了就j–，如果小了就i++，这样子可以完全遍历矩阵，最后实现时间65ms，还可以了
class Solution { public: bool searchMatrix(vector<vector<int>>& matrix, int target) { int m =matrix.size(); if(m==0) return false; int n = matrix[0].size(); int i =0,j=n-1; while(i<m && j>=0){ if(matrix[i][j] == target) return true; else if(matrix[i][j] > target) j--; else i++; } return false; } };