最短路默写

Dij

        bool visit[MAXN];
        priority_queue<pair<int, int>, vector<pair<int, int> >, greater<pair<int, int> > > que;
        pair<int, int> cnt;
        memset(visit, false, sizeof(visit));
        visit[st] = true;
        que.push(make_pair(0, st));
        while (!que.empty())
        {
                cnt = que.top();
                que.pop();
                int ucost = cnt.first;
                int u = cnt.second;
                for (int i = Head[u]; i; i = nxt[i])
                {
                        int v = to[i];
                        if (visit[v])
                        {
                                continue;
                        }
                        visit[v] = true;
                        if (dis[v] > dis[u] + cost[i])
                        {
                                dis[v] = dis[u] + cost[i];
                                que.push(make_pair(dis[v], v));
                        }
                }
        }

SPFA

dfs求负环版

#include<bits/stdc++.h>
using namespace std;
const int maxn = 2e5+ 5;
struct lpl{ int to, dis; }lin;
vector<lpl> point[maxn];
int n, m, dis[maxn];
bool Flag, vis[maxn];

inline void connect(int a, int b, int w){ lin.to = b; lin.dis = w; point[a].push_back(lin); }

inline void putit()
{
    int a, b, w;
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; ++i) point[i].clear();
    for(int i = 1; i <= m; ++i)
    {
        scanf("%d%d%d", &a, &b, &w);
        connect(a, b, w);
        if(w > 0) connect(b, a, w);
    }
}

void SPFA(int t)
{
    int now; vis[t] = true;
    for(int i = point[t].size() - 1; i >= 0; --i)
    {
        now = point[t][i].to;
        if(dis[now] > dis[t] + point[t][i].dis)
        {
            dis[now] = dis[t] + point[t][i].dis;
            if(vis[now] == true || Flag == true) { Flag = true; break; }
            SPFA(now);
        }
    }
    vis[t] = false;
}

int main()
{
    int T; scanf("%d", &T);
    while(T--)
    {
        putit();
        memset(dis, 0, sizeof(dis)); memset(vis, false, sizeof(vis)); Flag = false;
        for(int i = 1; i <= n; ++i) { SPFA(i); if(Flag == true) break; }
        if(Flag == true) { printf("YE5\n"); continue;}
        printf("N0\n");
    }
    return 0;
}

 

        bool visit[MAXN];
        queue<int> que;
        memset(visit, false, sizeof(visit));
        dis[st] = 0, visit[st] = true;
        que.push(st);
        while (!que.empty())
        {
                int u = que.front();
                que.pop();
                visit[u] = false;
                for (int i = Head[u]; i; i = nxt[i])
                {
                        int v = to[i];
                        if (dis[v] > dis[u] + cost[i])
                        {
                                dis[v] = dis[u] + cost[i];
                                if (!visit[v])
                                {
                                        visit[v] = true;
                                        que.push(v);
                                }
                        }
                }
        }