LeetCode - Search Insert Position

Problem description

description

Given a sorted array 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 may assume no duplicates in the array.

Example 1:

Input: [1,3,5,6], 5
Output: 2

Example 2:

Input: [1,3,5,6], 2
Output: 1

Example 3:

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

Example 4:

Input: [1,3,5,6], 0
Output: 0

Analysis

Basic idea is to use binary search. If there is no target in the nums array, then left and right are going to fall into one position, there are two situation to escape from the while loop, if nums[mid] < target, then it should be inserted into index mid + 1, and if nums[mid] > target, then target should be inserted into index mid, so return left is always the right answer.

Here’s the code:

public class SearchInsertPosition {

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

    while (left <= right) {
      int mid = left + (right - left) / 2;

      if (nums[mid] == target) {
        return mid;
      } else if (nums[mid] < target) {
        left = mid + 1;
      } else if (nums[mid] > target) {
        right = mid - 1;
      }
    }

    return left;
  }
}

What to improve

• Binary Search Summary