Search a 2D Matrix II

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;}target_ = target;return searchMatrix(matrix, 0, 0, matrix.size() - 1, matrix[0].size() - 1);}bool searchMatrix(vector<vector<int>>& matrix, int x, int y, int xEnd, int yEnd) {if (x > xEnd || y > yEnd){return false;}int i = ((x + xEnd) >> 1);int j = ((y + yEnd) >> 1);vector<int> const & tmp = matrix[i];int val = tmp[j];if ( val == target_){return true;}if (target_ < val){    return   ( target_ >= tmp[y] && searchMatrix(matrix, i , y, xEnd, j - 1) )     ||  searchMatrix(matrix, x, y, i - 1, yEnd) ;} return  ( target_ <= tmp[yEnd] && searchMatrix(matrix, x, j + 1, i, yEnd) ) || searchMatrix(matrix, i+1, y, xEnd, yEnd) ;}int target_;};