【leetcode】search insert position

問題：

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

分析：

[1] 若target在array中，則返回index；

[2]若target不在array，找到插入位置；

[3]二分法，log(n).

代碼：

class Solution {
public:
    int searchInsert(vector<int>& nums, int target) {
        int first=0,last=nums.size()-1;
        while(first<=last){
            int mid=first+(last-first)/2;
            //二分
            if(nums[mid]<target){
                first=mid+1;
            }else{
                last=mid-1;
            }
        }
        return first;
    }
};