SPFA求最短路

Posted 2020-10-09

syzoj.com 最短路径问题

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <vector>
using namespace std;
#define maxn 10001
vector<int>a[maxn],b[maxn];
queue<int>bfs;
int dis[maxn];
inline int read(){
    int num=0,f=1; char c=getchar();
    while(!isdigit(c)){if(c==‘-‘) f=-1; c=getchar();}
    while(isdigit(c)){num=(num<<1)+(num<<3)+(c^48); c=getchar();}
    return num*f;
}
int n,m;
inline int in(){
    n=read(); m=read();
    for(int i=1;i<=m;i++){
        int u,v,c;
        u=read(); v=read(); c=read();
        a[u].push_back(v);
        b[u].push_back(c);
    }
}
inline int work(){
    memset(dis,127,sizeof(dis));
    dis[1]=0;
    bfs.push(1);
    while(!bfs.empty()){
        int city=bfs.front();
        bfs.pop();
        int num=a[city].size();
        for(int i=0;i<num;i++){
            int next=a[city][i];
            int next_c=b[city][i];
            dis[next]=min(dis[next],dis[city]+next_c);
            bfs.push(next);
        }
    }
}
inline int out(){
    cout<<dis[n];
}
int main(){
    in();
    work();
    out();
}