LeetCode 35. Search Insert Position

Question

Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You must write an algorithm with O(log n) runtime complexity.

Example 1:

Input: nums = [1,3,5,6], target = 5
Output: 2

Example 2:

Input: nums = [1,3,5,6], target = 2
Output: 1

Example 3:

Input: nums = [1,3,5,6], target = 7
Output: 4

Constraints:

• 1 <= nums.length <= 104
• -104 <= nums[i] <= 104
• nums contains distinct values sorted in ascending order.
• -104 <= target <= 104

Source: https://leetcode.com/problems/search-insert-position/

Solution

public int searchInsert(int[] nums, int target) {
    int len = nums.length;
    int left = 0, right = len - 1;

    // mid is rounded to the floor, so left must make progress
    while (left < right) {
        int mid = left + (right - left) / 2;
        if (nums[mid] == target) {
            return mid;
        } else if (nums[mid] > target) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }

    // out of the loop, left == right
    if (nums[left] == target) {
        return left;
    } else if (nums[left] < target) {
        return right + 1;
    } else {
        return left;
    }
}