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Leetcode034-findFirstAndLastPositionOfElementInSortedArray

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Solution Report of LeetCode Acceptted

Description

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

Example 1:

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Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]

Example 2:
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Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]

Solution

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class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums == null || nums.length == 0) return new int[]{-1, -1};
        int smallest = findSmall(nums, target);
        int highest = findHigh(nums, target);
        int[] res = new int[]{smallest, highest};
        return res;
    }
    private int findSmall(int[] nums, int target){
        int left = 0;
        int right = nums.length - 1;
        int res = -1;
        while(left <= right){
            int mid = (left + right) / 2;
            if (nums[mid] == target) res = mid;
            if (nums[mid] >= target)
                right = mid - 1;
            else left = mid + 1;
        }
        return res;
    }
    private int findHigh(int[] nums, int target){
        int left = 0;
        int right = nums.length - 1;
        int res = -1;
        while(left <= right){
            int mid = (left + right) / 2;
            if (nums[mid] == target) res = mid;
            if (nums[mid] <= target)
                left = mid + 1;
            else right = mid - 1;
        }
        return res;
    }
}