Question Definition
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.
Java Solution
public boolean searchMatrix(int[][] matrix, int target) {
if(matrix.length == 0 || matrix[0].length == 0) return false;
int i = 0;
int left = 0;
int right = matrix[0].length - 1;
while(true){
int mid = (left + right) / 2;
if(matrix[i][mid] == target)
return true;
if(matrix[i][mid] < target)
left = mid + 1;
else
right = mid - 1;
if(left > right){
if(left == 0)
return false;
if(i == matrix.length - 1)
return false;
i++;
left = 0;
right = matrix[i].length - 1;
}
}
}
Comments