bzoj 1975: [Sdoi2010]魔法猪学院 [k短路]-优快云博客

本文提供了一道名为“魔法猪学院”的算法题目解析，使用A*启发式搜索算法结合Dijkstra算法解决带权路径寻找问题。通过自定义优先级队列实现最短路径计算。

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1975: [Sdoi2010]魔法猪学院

裸题...

被double坑死了

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
typedef long long ll;
#define pdi pair<double, int>
#define fir first
#define sec second
const int N = 5005, M = 2e5+5;
inline int read(){
    char c=getchar(); int x=0,f=1;
    while(c<'0'||c>'9') {if(c=='-')f=-1;c=getchar();}
    while(c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
    return x*f;
}
 
int n, m, u, v, s, t; double en, w;
 
namespace I {
    struct edge {int v, ne; double w;} e[M];
    int cnt, h[N];
    inline void ins(int u, int v, double w) {
        e[++cnt] = (edge){v, h[u], w}; h[u] = cnt;
    }
    priority_queue<pdi, vector<pdi>, greater<pdi> > q;
    int vis[N];
    void dij(int s, int t, double *d) {
        for(int i=1; i<=n; i++) d[i] = 1e15, vis[i] = 0;
        d[s] = 0; q.push(make_pair(0, s));
        while(!q.empty()) {
            int u = q.top().sec; q.pop();
            if(vis[u]) continue; vis[u] = 1;
            for(int i=h[u];i;i=e[i].ne) {
                int v = e[i].v;
                if(d[v] > d[u] + e[i].w) 
                    d[v] = d[u] + e[i].w, q.push(make_pair(d[v], v));
            }
        }
    }
}
 
struct edge {int v, ne; double w;} e[M];
int cnt, h[N];
inline void ins(int u, int v, double w) {
    e[++cnt] = (edge){v, h[u], w}; h[u] = cnt;
}
double d_t[N]; int vis[N];
priority_queue<pdi, vector<pdi>, greater<pdi> > q;
void a_star(int s, int t) {
    I::dij(t, s, d_t);
    q.push(make_pair(d_t[s], s));
    while(!q.empty()) {
        int u = q.top().sec; double d = q.top().fir; q.pop();
        if(u == t) if((en -= d) < 0) return;
        vis[u]++;
        for(int i=h[u];i;i=e[i].ne) {
            int v = e[i].v;
            q.push(make_pair(d - d_t[u] + d_t[v] + e[i].w, v));
        }
    }
}
int main() {
    freopen("in", "r", stdin);
    n=read(); m=read(); scanf("%lf", &en); s=1; t=n;
    for(int i=1; i<=m; i++) u=read(), v=read(), scanf("%lf", &w), I::ins(v, u, w), ins(u, v, w);
    a_star(s, t);
    printf("%d\n", vis[t]);
}

转载于:https://www.cnblogs.com/candy99/p/6793141.html