CodeForces 【20C】Dijkstra？

解题思路

heap+Dijkstra就能过。注意边是双向边，要用long long。

附上代码

#include <iostream>
#include <queue>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

typedef pair<long long, int> P;
priority_queue<P, vector<P>, greater<P> > Q;
typedef long long LL;
const int maxnode = 1e5+3, maxedge = 2e5+5;
int n, m, u[maxedge], v[maxedge], fir[maxnode], nx[maxedge], pre[maxnode], Ans[maxnode];
LL w[maxedge], dis[maxedge], cnt, tot;
inline void addedge(int x, int y, LL z) {
    nx[++cnt] = fir[x];
    fir[x] = cnt;
    u[cnt] = x, v[cnt] = y, w[cnt] = z;
}
inline void Dijkstra() {
    fill(dis+1, dis+1+n, 2147483647000);
    Q.push(P(0, 1));
    dis[1] = 0;
    int k;
    while (!Q.empty()) {
        P x = Q.top();
        Q.pop();
        if(x.first > dis[x.second]) continue;
        k = fir[x.second];
        while (k != -1) {
            if(dis[u[k]] + w[k] < dis[v[k]]) {
                dis[v[k]] = dis[u[k]] + w[k];
                pre[v[k]] = u[k];
                Q.push(P(dis[v[k]], v[k]));
            }
            k = nx[k];
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);
    memset(fir, -1, sizeof(fir));
    int x, y; LL z;
    for(int i=1; i<=m; i++) {
        scanf("%d%d%lld", &x, &y, &z);
        addedge(x, y, z);
        addedge(y, x, z);
    }
    Dijkstra();
    if(dis[n] == 2147483647000) {
        printf("-1
");
        return 0;
    }
    for(int i=n; i>=1; i=pre[i]) {
        Ans[++tot] = i;
    }
    for(int i=tot; i>=1; i--) printf("%d ", Ans[i]);
}