【luogu P3371 单源最短路径 】 模板 SPFA优化

无优化：500ms

deque优化：400ms

#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 550000;
const int inf = 0x7fffffff;
int dis[maxn], n, m, s;
bool vis[maxn];
deque<int> q;
struct edge{
    int len, to, from, next;
}e[maxn<<2];
int cnt, head[maxn];
void add(int u, int v, int w)
{
    e[++cnt].from = u;
    e[cnt].len = w;
    e[cnt].next = head[u];
    e[cnt].to = v;
    head[u] = cnt;
}
void SPFA()
{
    while(!q.empty())
    {
        int now = q.front(); q.pop_front();
        vis[now] = 0;
        for(int i = head[now]; i != -1; i = e[i].next)
        {
            if(dis[e[i].to] > dis[now] + e[i].len)
            {
                dis[e[i].to] = dis[now] + e[i].len;
                if(!vis[e[i].to])
                {
                    vis[e[i].to] = 1;
                    if(q.empty()||dis[e[i].to] > dis[q.front()])
                    q.push_back(e[i].to);
                    else
                    q.push_front(e[i].to);
                }
            }
        }
    }
}
int main()
{
    memset(head, -1, sizeof(head));
    scanf("%d%d%d",&n,&m,&s);
    for(int i = 1; i <= n; i++)
    dis[i] = inf;
    for(int i = 1; i <= m; i++)
    {
        int u, v, w;
        scanf("%d%d%d",&u,&v,&w);
        add(u,v,w);
    }
    vis[s] = 1;
    dis[s] = 0;
    q.push_back(s);
    SPFA();
    for(int i = 1; i <= n; i++)
    printf("%d ",dis[i]);
    return 0;
}

priority_queue优化：300ms

#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define ll long long
using namespace std;
const ll maxn = 200000 + 10;
const ll inf = 2147483647;
inline ll read()
{
    ll k=0,f=1;
    char c=getchar();
    while(!isdigit(c))
    {
        if(c=='-')f=-1;
        c=getchar();
    }
    while(isdigit(c))
    {
        k=(k<<1)+(k<<3)+c-48;
        c=getchar();
    }
    return k*f;
}
ll n, m, k, s, end, dis[maxn];
bool vis[maxn];
struct edge{
    ll from, len, to, next;
}e[maxn<<2];
ll head[maxn], cnt = 0;
struct cmp{
    bool operator ()(int &x, int &y)
    {
        return dis[x] > dis[y];
    }
};
priority_queue<int, vector<int>, cmp> q;
void add(ll u, ll v, ll w)
{
    e[++cnt].from = u;
    e[cnt].to = v;
    e[cnt].len = w;
    e[cnt].next = head[u];
    head[u] = cnt;
}
void SPFA()
{
    //memset(dis, 127, sizeof(dis));
    memset(vis, 0, sizeof(vis));
    q.push(s);
    dis[s] = 0;
    vis[s] = 1;
    while(!q.empty())
    {
        int now = q.top(); q.pop();
        vis[now] = 0;
        for(ll i = head[now]; i != -1; i = e[i].next)
        {
            if(dis[e[i].to] > dis[now] + e[i].len)
            {
               dis[e[i].to] = dis[now] + e[i].len;
               if(vis[e[i].to] == 0)
               {
                  vis[e[i].to] = 1;
                  q.push(e[i].to);
               }
            }
        }
    }
}
int main()
{
    memset(head, -1, sizeof(head));
    n = read(); m = read(); s = read();
    for(int i = 1; i <= n; i++) dis[i] = inf;
    for(ll i = 1; i <= m; i++)
    {
        ll u, v, w;
        u = read(); v = read(); w = read();
        add(u, v, w);
    }
    SPFA();
    for(int i = 1; i <= n; i++)
    printf("%lld ",dis[i]);
    return 0;
}