LeetCode 35. Search Insert Position

原题链接在这里：https://leetcode.com/problems/search-insert-position/description/

题目：

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.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

题解：

二分法查找，若是loop中找到了就返回mid, 若是没有找到，跳出loop时，恰巧 l 会走到比target 大的index上, r会走到比target小的index上。

Time Complexity: O(log n). Space O(1).

AC Java:

 1 public class Solution {
 2     public int searchInsert(int[] nums, int target) {
 3         if(nums == null){
 4             throw new IllegalArgumentException("Invalid input array.");
 5         }
 6 
 7         int l = 0;
 8         int r = nums.length-1;
 9         while(l<=r){
10             int mid = l + (r-l)/2;
11             if(nums[mid] > target){
12                 r = mid-1;
13             }else if(nums[mid] < target){
14                 l = mid+1;
15             }else{
16                 return mid;
17             }
18         }
19         return l;
20     }
21 }