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 from left to right.
- The first integer of each row is greater than the last integer of the previous row. For example,
Consider the following matrix:
[
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
Given target = 3, return true.
My Java Solution
public boolean searchMatrix(int[][] matrix, int target) {
if(matrix.length == 0 || matrix[0].length == 0) return false;
int level = 0;
while(level < matrix.length){
if(target < matrix[level][0]) return false;
int left = 0;
int right = matrix[0].length - 1;
while(left <= right){
int mid = (left + right) / 2;
if(matrix[level][mid] == target) return true;
if(matrix[level][mid] > target)
right = mid - 1;
else
left = mid + 1;
}
level++;
}
return false;
}
Best Java Solution
public boolean searchMatrix(int[][] matrix, int target) {
int i = 0, j = matrix[0].length - 1;
while (i < matrix.length && j >= 0) {
if (matrix[i][j] == target) {
return true;
} else if (matrix[i][j] > target) {
j--;
} else {
i++;
}
}
return false;
}
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