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.
//算法思想: 逐行扫描matrix,对每一行进行二分查找 class Solution { public: bool binarySearch(vector<int>& vec,int target){ int front=0; int rear=vec.size()-1; int mid=0; while(front<=rear){ mid=(front+rear)/2; if(target<vec[mid]) rear=mid-1; else if(target>vec[mid]) front=mid+1; else return true; }//while return false; } bool searchMatrix(vector<vector<int>>& matrix, int target) { for(vector<vector<int>>::size_type i=0;i!=matrix.size();++i) if(binarySearch(matrix[i],target)) return true; return false; } };
