题目描述

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

思路

看到此题目的直觉想法就是使用二分查找法解决，然后就是根据上面的例子，好好在草稿子上画一画就可以搞定了。

代码

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public int searchInsert(int[] nums, int target) {
     if (null == nums || nums.length == 0) {
    	 return 0;
     }
     if (nums[0] > target) {
    	 return 0;
     }
     if (nums[nums.length - 1] < target) {
    	 return nums.length;
     }
     int lo = 0;
     int hi = nums.length - 1;
     while (lo <= hi) {
    	 int mid = lo + (hi - lo) / 2;
    	 if (nums[mid] == target) {
    		 return mid;
    	 } else if (nums[mid] > target) {
    		 hi = mid - 1;
    	 } else {
    		 lo = mid + 1;
    	 }
     }
     return lo;
 }