POJ 3463 Sightseeing

#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;

const int N = 1005;
const int M = 10005;

int testCase, n, m, tot = 0, head[N];
int dis1[N], cnt1[N], dis[N][2], cnt[N][2];
bool vis[N][2];

struct Edge {
    int to, nxt, val;
} e[M];

inline void add(int from, int to, int val) {
    e[++tot].to = to;
    e[tot].val = val;
    e[tot].nxt = head[from];
    head[from] = tot;
}

inline void read(int &X) {
    X = 0; char ch = 0; int op = 1;
    for(; ch > ‘9‘|| ch < ‘0‘; ch = getchar())
        if(ch == ‘-‘) op = -1;
    for(; ch >= ‘0‘ && ch <= ‘9‘; ch = getchar())
        X = (X << 3) + (X << 1) + ch - 48;
    X *= op;
}

struct Node {
    int now, s, d;
    
    inline Node(int nowNode, int sta, int dist) {
        now = nowNode, s = sta, d = dist;
    }
    
    friend bool operator < (const Node &x, const Node &y) {
        return x.d > y.d;
    }
    
};
priority_queue <Node> Q; 

void dij(int st) {
    memset(dis, 0x3f, sizeof(dis));
    memset(cnt, 0, sizeof(cnt));
    memset(vis, 0, sizeof(vis));
    
    Q.push(Node(st, 0, 0));
    dis[st][0] = 0, cnt[st][0] = 1;
    
    for(; !Q.empty(); ) {
        int x = Q.top().now, s = Q.top().s; Q.pop();
        
        if(vis[x][s]) continue;
        vis[x][s] = 1;
        
        for(int i = head[x]; i; i = e[i].nxt) {
            int y = e[i].to;
            if(dis[y][0] > dis[x][s] + e[i].val) {
                dis[y][1] = dis[y][0], cnt[y][1] = cnt[y][0];
                dis[y][0] = dis[x][s] + e[i].val;
                cnt[y][0] = cnt[x][s];
                Q.push(Node(y, 0, dis[y][0])), Q.push(Node(y, 1, dis[y][1]));
            } else if(dis[y][0] == dis[x][s] + e[i].val) {
                cnt[y][0] += cnt[x][s];
            } else if(dis[y][1] > dis[x][s] + e[i].val) {
                    dis[y][1] = dis[x][s] + e[i].val;
                    cnt[y][1] = cnt[x][s];
                    Q.push(Node(y, 1, dis[y][1]));
            } else if(dis[y][1] == dis[x][s] + e[i].val) 
                    cnt[y][1] += cnt[x][s];
        }
    }
}

int main() {
    for(read(testCase); testCase--; ) {
        read(n), read(m);
        
        tot = 0; memset(head, 0, sizeof(head));
        for(int x, y, v, i = 1; i <= m; i++) {
            read(x), read(y), read(v);
            add(x, y, v);
        }
        
        int st, ed;
        read(st), read(ed);
        dij(st);
        
        int ans = cnt[ed][0];
        if(dis[ed][1] - 1 == dis[ed][0]) ans += cnt[ed][1];
        printf("%d\n", ans);
     }
     return 0;
}