【Search Insert Position 】cpp

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

代码：

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

tips：

二分查找。如果没有找到，注意返回的值是begin还是end，找几个corner case测试一下。

===========================================

第二次过这道题，二分查找。找一侧的边界。

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