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34. Find First and Last Position of Element in Sorted Array
Medium
Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.
If target is not found in the array, return [-1, -1].
You must write an algorithm with O(log n) runtime complexity.
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]
Example 3:
Input: nums = [], target = 0
Output: [-1,-1]
Constraints:
0 <= nums.length <= 105-109 <= nums[i] <= 109numsis a non-decreasing array.-109 <= target <= 109
Solution
public class Solution {
public int[] SearchRange(int[] nums, int target) {
int[] ans = new int[2];
ans[0] = Helper(nums, target, false);
ans[1] = Helper(nums, target, true);
return ans;
}
private int Helper(int[] nums, int target, bool equals) {
int l = 0;
int r = nums.Length - 1;
int result = -1;
while (l <= r) {
int mid = l + (r - l) / 2;
if (nums[mid] == target) {
result = mid;
}
if (nums[mid] < target || (nums[mid] == target && equals)) {
l = mid + 1;
} else {
r = mid - 1;
}
}
return result;
}
}