leetCode 35.Search Insert Position (搜索插入位置) 解题思路和方法

Search Insert Position

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

思路：题目还是比较简单的，线性时间内可用循环遍历，不过也可以用二分查找，这样lgn的时间复杂度。

本文用二分实现，具体代码如下：

public class Solution {
public int searchInsert(int[] nums, int target) {
//特殊情况
if(nums.length == 0 || nums[0] > target)
return 0;
if(nums[nums.length - 1] < target)
return nums.length;
//先二分查找，找到了就返回
int low = 0;
int hight = nums.length - 1;
int mid = 0;
while(low <= hight){
mid = (low + hight)/2;
if(nums[mid] < target){
low = mid + 1;
}else if(nums[mid] > target){
hight = mid - 1;
}else{
return mid;
}
}
//找不到再判断与nums[mid]大小，返回索引
return nums[mid] > target?mid:mid+1;
}
}