#include <stdio.h>

#include<map>

using namespace std;

int main(){

int n;

while(scanf("%d",&n)!=EOF){

    map<long long,int> m;

for(int i =0;i<n;i++){

long long x;

scanf("%lld",&x);

m[x]++;

}

map<long long,int>::iterator it;

for(it=m.begin();it!=m.end();it++)

{

if(it->second==1){

printf("%lld\n",it->first);

break;}

}

}

return 0;

}

注意

map标准对象的运用：

map遍历：

for(map<int, string>::iterator it=map1.begin(); it!=map1.end(); it++)

 {

 cout << it->first << ":"<< it->second << endl;

 }

查找

string value1 = map1[2];

if(value1.empty())

{cout << "not found"<< endl;}

//方法2

map<int, string>::iterator it = map1.find(2);

if(it == map1.end())

{cout << "not found"<< endl;}

else  {cout << it->first << ":"<< it->second << endl;}