[LeetCode]035-Search Insert Position

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

Solution:
思路，改进的二分查找，有意思的是当这个数不在数列里时，在二分查找的终止返回条件里(left > right)，return left，即是它插入的位置。
在纸上画一画就能得出结论。

    int searchInsert(vector<int>& nums, int target) 
    {
        int n = nums.size();
        int left = 0;
        int right = n-1;
        return Binary_Search(nums,left,right,target);
    }
    int Binary_Search(vector<int>& nums,int left,int right,int target)
    {
        if(left <= right)
        {
            int mid = (left+right)/2;
            if(nums[mid] == target)
                return mid;
            else if(nums[mid] < target)
                Binary_Search(nums,mid+1,right,target);
            else
                Binary_Search(nums,left,mid-1,target);
        }
        else
            return left;
    }