35. Search Insert Position

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本文介绍了一个查找并返回目标值在已排序数组中应插入位置的算法。该算法首先检查数组边界情况，然后使用二分搜索法确定插入位置。示例包括不同输入下目标值的正确插入位置。

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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.

Example 1:

Input: [1,3,5,6], 5
Output: 2

Example 2:

Input: [1,3,5,6], 2
Output: 1

Example 3:

Input: [1,3,5,6], 7
Output: 4

Example 1:

Input: [1,3,5,6], 0
Output: 0

#include <iostream>  
#include <vector>

using namespace std; 

class Solution {
public:
	int searchInsert(vector<int>& nums, int target) {
		if (!nums.size()) return 0; 
		int left, right, index = -1;  
		right = nums.size() - 1; 
		left = 0;
		if (nums[left] > target) { return left; }
		if (nums[right] < target) { return right + 1 ; }
		if (search( nums,target, left, right, index))
			return index;
		else return left; 
		
	}
private: 
	bool	search(vector<int>& nums, int target,int & left, int & right, int & index)
	{
		int mid; 
		while (left <= right)
		{
			mid = (left + right) / 2;

			if (nums[mid] == target)
			{
				index = mid; 
				return true; 
			}
			if (nums[mid] > target) right= mid -1 ;
			else  left = mid +1 ; 
		}
		return false; 
	}
};

int main()
{
	vector<int> aa = { 1, 3, 5, 6 };
	Solution a;
	cout << a.searchInsert(aa, 3);
	system("pause"); 
	return 0;
}