[LeetCode] Search Insert Position

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

解题思路：

这道题较为简单，二分法查找即可。需要注意的是在没有命中的情况下返回的值。根据例子可以分析，若未命中，当前middle的值若比目标值大，则返回middle值，若比目标值小，返回middle+1。下面是代码：

class Solution {
public:
    int searchInsert(int A[], int n, int target) {
        int start=0, end = n-1;
        int middle;
        while(start <= end){
            middle=(start+end)/2;
            if(A[middle]==target){
                return middle;
            }
            if(A[middle]>target){
                end = middle-1;
            }else{
                start = middle + 1;
            }
        }
        if(A[middle]>target){
            return middle;
        }else{
            return middle+1;
        }
    }
};