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最新推荐文章于 2021-06-08 14:34:49 发布

原创最新推荐文章于 2021-06-08 14:34:49 发布 · 933 阅读

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#iterator #include #pair

本文介绍了一个比赛配对算法，该算法使用C++实现，并利用了multimap数据结构来存储选手的实力和ID。通过查找和比较选手实力范围内的数据，算法能够为每个新加入的选手找到最合适的配对对手。

//upper_bound Returns the first elment beyond the range

# include <iostream>
# include <cstdio>
# include <map>
# include <cmath>

using namespace std;

multimap<int,int> member;

int findMin(multimap<int,int>::iterator& start, multimap<int,int>::iterator& end) //找到区间中最小id
{
	multimap<int,int>::iterator i;
	int min = 1000000001;
	for ( i = start; i != end; i++ )
	{
		if ( i->second < min )
		{
			min = i->second;
		}
	}
	return min;
}

int findMinEXPT(multimap<int,int>::iterator& start, multimap<int,int>::iterator& end, int id)	//找到除本身外的最小id
{
	multimap<int,int>::iterator i;
	int min = 1000000001;
	for ( i = start; i != end; i++ )
	{
		if ( i->second < min && i->second != id )
		{
			min = i->second;
		}
	}
	return min;
}

multimap<int,int>::iterator findPos(int p,int id)
{
	multimap<int,int>::iterator i;
	for ( i = member.lower_bound(p); i != member.upper_bound(p); i++ )
	{
		if ( i->second == id )
		{
			return i;
		}
		
	}
	return member.end();
}



void match(int p,int id)
{
	int matchID = 0;
	int matchID_sub = 0;
	int lower = 0;
	int upper = 0;
	multimap<int,int>::iterator i;
	multimap<int,int>::iterator j;
	multimap<int,int>::iterator k;
	j = member.lower_bound(p);
	k = member.upper_bound(p);
	k--;
	if ( j != member.end() && k != member.end() )
	{

		if ( j == k )	//There is only one element that has the power p
		{
			if ( j == member.begin() )	//插入元素是第一个，则只需寻找其后满足条件的答案
			{
				i = j;
				k++;
				j++;
				k = member.upper_bound(k->first);
				matchID = findMin(j,k);
				printf("%d %d\n",i->second,matchID);
			}
			else	//插入元素不是第一个，则需要两头寻找
			{
				i = j;
				j--;
				k++;
				lower = i->first - j->first;
				upper = k->first - i->first;
				if ( lower < upper )	//如果左邻实力更接近，则寻找左邻中id最小的
				{
					j = member.lower_bound(j->first);
					matchID = findMin(j,i);
					printf("%d %d\n",i->second,matchID);

				}
				else if ( lower > upper )
				{
					j++;
					j++;
					k = member.upper_bound(k->first);
					matchID = findMin(j,k);
					printf("%d %d\n",i->second,matchID);
				}
				else	//如果两遍实力相差一样，那么就在两个区间的并集中寻找id最小的
				{
					int currentID = i->second;
					int downRange = j->first;
					int upRange = k->first;
					j = member.lower_bound(downRange);
					k = member.upper_bound(upRange);
					matchID = findMin(j,i);
					j = i;
					j++;
					matchID_sub = findMin(j,k);
					int finalMatch = min(matchID,matchID_sub);
					printf("%d %d\n",currentID,finalMatch);
					
				}
			}
		}
		else	//如果有多个选手实力与新手相等，那么在这些人中找id最小的即可
		{
			k++;
			i = findPos(p,id);
			matchID = findMinEXPT(j,k,i->second);
			printf("%d %d\n",i->second,matchID);
		}
	}
	else return;
}

int main()
{
	int n = 0;
	int id = 0;
	int power = 0;
	cin >> n;
	member.insert(make_pair(1000000000,1));
	for ( int i = 0; i < n; i++ )
	{
		scanf("%d%d",&id,&power);
		member.insert(make_pair(power,id));
		match(power,id);
	}
	return 0;
}