Difficulty: 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 from left to right.
- The first integer of each row is greater than the last integer of the previous row.
Example 1:
Input:
matrix = [
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
target = 3
Output: true
Example 2:
Input:
matrix = [
[1, 3, 5, 7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]
target = 13
Output: false
Language: Java
class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
if (matrix == null || matrix.length == 0) {
return false;
}
int rows = matrix.length;
int width = matrix[0].length;
if (width == 0) {
return false;
}
int targetRowIndex = -1;
for (int i = 0; i < rows; i++) {
if (matrix[i][0] <= target && matrix[i][width - 1] >= target) {
targetRowIndex = i;
break;
}
}
if (targetRowIndex < 0) {
return false;
}
int[] targetRow = matrix[targetRowIndex];
int left = 0;
int right = width;
int medium;
while (left < right) {
medium = (left + right) / 2;
if (targetRow[medium] == target) {
return true;
} else if (targetRow[medium] > target) {
right = medium;
} else {
left = medium + 1;
}
}
return false;
}
}