11374】Airport Express
阿新 • • 發佈:2018-12-17
題目意思就是有n個站點,要從s前往e,有經濟路線和商務路線,只能坐一次商務路線,求花費的最優解。
只要列舉選擇哪一條商務路線就好了,所以兩遍Dijkstra,一遍是從起點開始,一遍是從終點開始。如果需要使用由a站到b站的商務車票,則總開銷就是起點到a的開銷+商務路線開銷+b到終點的開銷。經過的站點就注意哪裡需要倒序輸出就行。格式卡了好幾次。。每組資料後要換行,行末不能有多餘空格。
要去青島了,也沒個底。。最近也沒寫幾道題,唉
/* * @Author: SamsonHo * @Date: 2018-10-20-23.06.40 * @URL:https://vjudge.net/problem/UVA-11374 */ #include<bits/stdc++.h> #define INF 0x3f3f3f3f using namespace std; typedef long long LL; const int MAXN = 1e5+10; int g[505][505],dis1[505],dis2[505],pre1[505],pre2[505],vis[505]; int n,kase = 0; stack<int> st; void Dijkstra(int s,int dis[],int pre[]) { for(int i = 0; i <= n; ++i) { dis[i] = INF; vis[i] = 0; pre[i] = -1; } dis[s] = 0; pre[s] = -1; for(int i = 1; i <= n; ++i) { int Min = INF,pos = -1; for(int j = 1; j <= n; ++j) { if(!vis[j] && dis[j] < Min) { Min = dis[j]; pos = j; } } if(pos == -1) break; vis[pos] = 1; for(int j = 1; j <= n; ++j) { if(!vis[j] && dis[j]>dis[pos]+g[pos][j]) { dis[j] = g[pos][j]+dis[pos]; pre[j] = pos; } } } } int main(void) { int u,v,c,eco,com,s,e; while(~scanf("%d%d%d",&n,&s,&e)) { for(int i = 0; i <= n; ++i) for(int j = 0; j <= n; ++j) g[i][j] = i==j?0:INF; scanf("%d",&eco); for(int i = 1; i <= eco; ++i) { scanf("%d%d%d",&u,&v,&c); g[u][v] = g[v][u] = c; } Dijkstra(s,dis1,pre1); Dijkstra(e,dis2,pre2); scanf("%d",&com); int pos = -1,tmp,a,b,ans = dis1[e]; //先將ans初始化為不需要使用車票的花費 for(int i = 1;i <= com; ++i) { scanf("%d%d%d",&u,&v,&c); tmp = dis1[u]+dis2[v]+c; if(ans > tmp) { ans = tmp; pos = u; a = u,b = v; } tmp = dis1[v]+dis2[u]+c; if(ans > tmp) { pos = v; ans = tmp; a = v,b = u; } } if(kase++) puts(""); if(pos == -1) //不需要使用商務路線 { while(!st.empty()) st.pop(); for(int i = e; i != -1; i = pre1[i]) st.push(i); while(!st.empty()) { printf("%d",st.top()); st.pop(); if(st.empty()) printf("\n"); else printf(" "); } puts("Ticket Not Used"); } else { while(!st.empty()) st.pop(); for(int i = a; i!=-1; i = pre1[i]) st.push(i); int flag = 1; while(!st.empty()) { if(flag) flag = 0; else printf(" "); printf("%d",st.top()); st.pop(); } for(int i = b; i != -1; i = pre2[i]) printf(" %d",i); puts(""); printf("%d\n",pos); } printf("%d\n",ans); } }