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①c++完整代码 采用find函数：

#include<algorithm>
#include<vector>
#include<iostream>
using namespace std;

class Solution {
public:
    int search(vector<int>& nums, int target) {
    vector<int>::iterator index_iterator=find(nums.begin(),nums.end(),target);
	//find返回的是迭代器,如果没找到，返回的是nums.end()，即最后一个元素的下一个地址 
    int index=index_iterator-nums.begin();
    //vevtor 是size() 
	if(index>=nums.size())  cout<<-1;
	else cout<<index;

    }
};

int main(){
	vector<int> sz;int n;int t;int i;
	cin>>n;
	while(n--)
	{
		cin>>i;
		sz.push_back(i);
	}
	cin>>t;
	Solution y;
	y.search(sz,t);
	
}

②采用二分查找

#include<algorithm>
#include<vector>
#include<iostream>
using namespace std;

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

    }
};

int main(){
	vector<int> sz;int n;int t;int i;
	cin>>n;
	while(n--)
	{
		cin>>i;
		sz.push_back(i);
	}
	cin>>t;
	Solution y;
	int result=y.search(sz,t);
	cout<<result;
	
}