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[0].empty())
return false;
if (matrix.front().front() > target || matrix.back().back() < target)
return false;
int row = matrix.size(), col = matrix[0].size();
int i = 0, j = col-1;
while (i < row && j >= 0) {
if (matrix[i][j] == target)
return true;
else if (matrix[i][j] > target)
j --;
else
i ++;
}
return false;
}
};