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.
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() || matrix[].empty()) return false;
if (target < matrix[][] || target > matrix.back().back()) return false;
int x = matrix.size() - , y = ;
while (true) {
if (matrix[x][y] > target) --x;
else if (matrix[x][y] < target) ++y;
else return true;
if (x < || y >= matrix[].size()) break;
}
return false;
}
};