10986-Sending email // Bellman-Ford

Question analysis: the bare shortest path, but there are a lot of nodes. The adjacent matrix will be RE, and the graph will be stored in the adjacent linked list. Then BallmanFord went on.

Vomit: first, I didn't read the data and RESS all the time. Then, when I output the data, I reversed it with the number. I 've been WA, wow!

Code:

#include<cstdio>#include<cstring>#include<vector>#include<queue>using namespace std;const int INF = 2000000010;const int maxn = 2*50005;int u[maxn],v[maxn],w[maxn];int first[maxn],next[maxn];int n,m,s,t;queue<int> q;bool inq[maxn];int d[maxn];void Bellman_Ford(){    for(int i = 0; i < n; i++) d[i] = INF,inq[i] = false;    d[s] = 0;    q.push(s); inq[s] = true;    while(!q.empty())    {        int x = q.front(); q.pop();        inq[x] = false;        for(int e = first[x]; e != -1; e = next[e])        {            if(d[v[e]] > d[x] + w[e])            {                d[v[e]] = d[x] + w[e];                if(!inq[v[e]])                {                    inq[v[e]] = true;                    q.push(v[e]);                }            }        }    }}int main(){    int N;    scanf("%d",&N);    for(int k = 1; k <= N; k++)    {        scanf("%d%d%d%d",&n,&m,&s,&t);        for(int i = 0; i < n; i++) first[i] = -1;        for(int e = 0,i = 0; i < m; e += 2,i++)        {            scanf("%d%d%d",&u[e],&v[e],&w[e]);            next[e] = first[u[e]];            first[u[e]] = e;            u[e+1] = v[e];            v[e+1] = u[e];            w[e+1] = w[e];            next[e+1] = first[v[e]];            first[v[e]] = e + 1;        }        Bellman_Ford();        printf("Case #%d: ",k);        if(d[t] != INF) printf("%d\n",d[t]);        else printf("unreachable\n");    }    return 0;}