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.

class Solution {public:bool searchMatrix(vector<vector<int>>& matrix, int target) {if(matrix.empty())return false;if(matrix[0].empty())return false;if(matrix[0][0]>target||matrix[matrix.size()-1][matrix[0].size()-1]<target)return false;int curX=0,curY=0;bool horizontal=true;while(curX!=matrix[0].size()&&curY!=matrix.size()){if(horizontal){while(curX!=matrix[0].size()&&matrix[curY][curX]<target)curX++;if(curX==matrix[0].size()||matrix[curY][curX]>target){curX--;horizontal=false;curY++;}elsereturn true;}else{while(curY!=matrix.size()&&matrix[curY][curX]<target)curY++;if(curY==matrix.size()||matrix[curY][curX]>target){if(curY==matrix.size()&&matrix[curY-1][curX]<target)return false;curY--;horizontal=false;curX--;}elsereturn true;}}return false;}};

accepted