B - Median-----（2015 summer training #8(Qualifying)）

B - Median
时限:5000MS 内存:65536KB 64位IO格式:%lld
& %llu

问题描述

The median of m numbers is after sorting them in order, the middle one number of them if m is even or the average number of the middle 2 numbers if m is
odd. You have an empty number list at first. Then you can add or remove some number from the list.
For each add or remove operation, output the median of the number in the list please.

输入

This problem has several test cases. The first line of the input is an integer T (0<T<=100) indicates the number of test cases. The first line of each
test case is an integer n (0<n<=10000) indicates the number of operations. Each of the next n lines is either "add x" or "remove x"(-231<=x<231)
indicates the operation.

输出

For each operation of one test case: If the operation is add output the median after adding x in a single line. If the operation is removeand
the number x is not in the list, output "Wrong!" in a single line. If the operation is remove and the number x is in the list, output the median after deleting x in a single
line, however the list is empty output "Empty!".

样例输入

2
7
remove 1
add 1
add 2
add 1
remove 1
remove 2
remove 1
3
add -2
remove -2
add -1

样例输出

Wrong!
1
1.5
1
1.5
1
Empty!
-2
Empty!
-1

Hint

if the result is an integer DO NOT output decimal point. And if the result is a double number , DO NOT output trailing 0s.

分析：看了这道题，学习了容器multiset，收获还是蛮多的。然而并没有AC。

CODE：

#include <iostream>
#include <string.h>
#include <set>
#include <cstdio>
using namespace std;

int main()
{
int t;
cin>>t;
while(t--){
int n;
//        cin>>n;
scanf("%d",&n);
//        string s;
char s[10];
int num;
multiset<int> arr;
multiset<int>::iterator it;
it=arr.begin();
bool vis=false;
while(n--){
//            cin>>s>>num;
scanf("%s",s);
scanf("%d",&num);
if(!strcmp(s,"remove")){
int len=arr.size();
multiset<int>::iterator itt;
itt=arr.find(num);
if(*it==num){
itt=it;
if(arr.size()&1)
it++;
else
it--;
}
if(itt!=arr.end())
arr.erase(itt);
else{
cout<<"Wrong!"<<endl;
continue;
}
if(arr.empty()){
cout<<"Empty!"<<endl;
continue;
}
}
else{
arr.insert(num);
if(!vis){
it=arr.begin();
vis=true;
}
else if((arr.size()&1)&&num<*it)
it--;
else if(arr.size()%2==0&&num>*it)
it++;
}
int len=arr.size();
if(len&1)
//                cout<<*it<<endl;
printf("%d\n",*it);
else{
multiset<int>::iterator tmp;
tmp=it;
int a=*it,b=*(--tmp);
long long ans=(a+b)/2.0;
//                cout<<ans<<endl;
if((a+b)%2==0)
printf("%lld\n",ans);
else if(a+b==-1)
printf("-0.5\n");
else
printf("%lld.5\n",ans);
}
}
memset(s,0,sizeof(s));
//        arr.~multiset();
arr.clear();
}
return 0;
}