Find First and Last Position of Element in Sorted Array
Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.
Your algorithm's runtime complexity must be in the order of O(log n).
If the target is not found in the array, return [-1, -1].
Example 1:
Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]
Example 2:
Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]
Solution:
class Solution {
public int[] searchRange(int[] nums, int target) {
return new int[]{first(nums, target), last(nums, target)};
}
private int first(int[] nums, int target) {
if (nums == null || nums.length == 0) return -1;
int left = 0;
int right = nums.length - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (nums[mid] > target) {
right = mid - 1;
} else if (nums[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
if (left >= nums.length || nums[left] != target) return -1;
return left;
}
private int last(int[] nums, int target) {
if (nums == null || nums.length == 0) return -1;
int left = 0;
int right = nums.length - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (nums[mid] > target) {
right = mid - 1;
} else if (nums[mid] < target) {
left = mid + 1;
} else {
left = mid + 1;
}
}
if (right < 0 || nums[right] != target) return -1;
return right;
}
}