HDU 5876 Sparse Graph 大连网络赛

题意补图上求每个节点从source的深度，到达不了就深度为-1，依次输出。就是个补图bfs...............mdzz

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <set>
using namespace std;
const int MAXE = 200005;

struct Edge
{
	int from, to;
	int next;
}edge[MAXE];

struct Node
{
	int v;
	int step;
}tmp;

int cnt;
int head[200005];
int d[200005];
int n, m;
int source;
set<int>::iterator it;

void addedge(int u, int v)
{
	edge[cnt].next = head[u];
	edge[cnt].from = u;
	edge[cnt].to = v;
	head[u] = cnt++;
	edge[cnt].next = head[v];
	edge[cnt].from = v;
	edge[cnt].to = u;
	head[v] = cnt++;
}

void bfs(int s)
{
	Node u;
	int v;
	set<int> a;
	set<int> b;
	queue<Node> q;
	tmp.v = s;
	tmp.step = 0;
	q.push(tmp);

	for (int i = 1; i <= n; i++)
	{
		if (i == s) continue;
		a.insert(i);
	}
	while (!q.empty())
	{
		u = q.front();
		q.pop();
		
		for (int i = head[u.v]; i != -1; i = edge[i].next)
		{
			v = edge[i].to;
			if (a.count(v))
			{
				a.erase(v);
				b.insert(v);
			}
		}

		for (it = a.begin(); it != a.end(); it++)
		{
			tmp.v = *it;
			tmp.step = u.step + 1;
			d[*it] = tmp.step;
			q.push(tmp);
		}
		a.swap(b);
		b.clear();
	}
}

int main(void)
{
	int T;
	scanf("%d", &T);
	while (T--)
	{
		scanf("%d%d", &n, &m);
		cnt = 0;
		memset(head, -1, sizeof head);
		memset(d, -1, sizeof d);
		int l, r;
		for (int i = 0; i < m; i++)
		{
			scanf("%d%d", &l, &r);
			addedge(l, r);
		}
		scanf("%d", &source);
		int flag = 1;
		bfs(source);
		if (source != 1)
		{
			printf("%d", d[1]);
			flag = 0;
		}
		for (int i = 2; i <= n; i++)
		{
			if (source == i) continue;
			if (flag == 0) printf(" ");
			printf("%d", d[i]);
			flag = 0;
		}
		printf("\n");
	}
	return 0;
}