LightOJ1074 SPFA判負環

不怎麼會SPFA，當模板用吧

複雜度O（ke）k約等於2

用cir［］數組紀錄有沒有負環

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
using namespace std;
#define FOR(i,j,k) for(int i=j;i<=k;i++)
const int N = 220;
const int inf= 0x3f3f3f3f;
struct Edge
{
    int v,cost;
    Edge(int _v = 0, int _cost = 0):v(_v),cost(_cost){}
};
vector<Edge>E[N];
void addedge(int u,int v,int w)
{
    E[u].push_back(Edge(v,w));
}
bool vis[N];
int cnt[N];
int d[N];
bool cir[N];
int n;
void dfs(int u)
{
    cir[u] = true;
    for(int i = 0;i < E[u].size();i++)
        if(cir[E[u][i].v]==0)
            dfs(E[u][i].v);
}

void SPFA(int start)
{
    memset(vis,false,sizeof(vis));
    for(int i = 1;i <= n;i++)
        d[i]=inf;
    vis[start]=true;
    d[start] = 0;
    queue<int>que;
    while(!que.empty())
        que.pop();
    que.push(start);
    memset(cnt,0,sizeof(cnt));
    cnt[start] = 1;
    memset(cir,false,sizeof(cir));
    while(!que.empty())
    {
        int u = que.front();
        que.pop();
        vis[u] = false;
        for(int i = 0;i < E[u].size();i++)
        {
            int v = E[u][i].v;
            if(cir[v])continue;
            if(d[v] > d[u] + E[u][i].cost)
            {
                d[v] = d[u] + E[u][i].cost;
                if(vis[v]==0)
                {
                    vis[v] = true;
                    que.push(v);
                    cnt[v]++;
                    if(cnt[v]>n)
                    dfs(v);
                }
            }
        }
    }
}
int a[N];
int main()
{
    int t;
    cin>>t;
    FOR(z,1,t)
    {
        scanf("%d",&n);
        FOR(i,1,n)
            E[i].clear();
        FOR(i,1,n)
            scanf("%d",&a[i]);
        int m;
        scanf("%d",&m);
        while(m--)
        {
            int a1,b1;
            scanf("%d%d",&a1,&b1);
            addedge(a1,b1,(a[b1]-a[a1])*(a[b1]-a[a1])*(a[b1]-a[a1]));
        }
        SPFA(1);
        scanf("%d",&m);
        int u;
        printf("Case %d:\n",z);
        while(m--)
        {
            scanf("%d",&u);
            if(d[u]==inf||d[u]<3||cir[u]==1)
                cout<<"?"<<endl;
            else cout<<d[u]<<endl;
        }
    }
    return 0;
}