Leetcode 240. Search a 2D Matrix II (Medium) (cpp)

Leetcode 240. Search a 2D Matrix II (Medium) (cpp)

Tag: Binary Search, Divide and Conquer

Difficulty: Medium

/*

240. Search a 2D Matrix II (Medium)

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) {
int r = matrix.size() - 1, c = matrix[0].size() - 1;
int i = 0, j = c;
while (i <= r && j >= 0) {
if (matrix[i][j] > target) j--;
else if (matrix[i][j] < target) i++;
else return true;
}
return false;
}
};