PATA1111题解

两次Dijkstra + DFS

//
//  main.cpp
//  PATA1111
//
//  Created by Phoenix on 2018/2/23.
//  Copyright © 2018年 Phoenix. All rights reserved.
//

#include <iostream>
#include <cstdio>
#include <queue>
#include <vector>
using namespace std;
const int maxn = 510;
const int inf = 1000000000;
int n, m, st, ed;
int G[maxn][maxn], T[maxn][maxn];
int d[maxn], t[maxn];
bool vis[maxn] = {false}, vis1[maxn] = {false};
vector<int> pre[maxn], pre1[maxn];

void dijkstra1(int s){
    fill(d, d + maxn, inf);
    d[s] = 0;
    for(int i = 0; i < n; i++) {
        int u = -1, MIN = inf;
        for(int j = 0; j < n; j++) {
            if(vis[j] == false && d[j] < MIN) {
                u = j;
                MIN = d[j];
            }
        }
        if(u == -1) return;
        vis[u] = true;
        for(int v = 0; v < n; v++) {
            if(vis[v] == false && G[u][v] != inf) {
                if(d[u] + G[u][v] < d[v]) {
                    pre[v].clear();
                    d[v] = d[u] + G[u][v];
                    pre[v].push_back(u);
                } else if(d[u] + G[u][v] == d[v]) {
                    pre[v].push_back(u);
                }
            }
        }
    }
}

vector<int> temp, path;
int optvalue = inf;
void DFS(int v) {
    if(v == st) {
        temp.push_back(v);
        int value = 0;
        for(int i = temp.size() - 1; i > 0; i--) {
            value += T[temp[i]][temp[i - 1]];
        }
        if(value < optvalue) {
            optvalue = value;
            path = temp;
        }
        temp.pop_back();
    }
    temp.push_back(v);
    for(int i = 0; i < pre[v].size(); i++) {
        DFS(pre[v][i]);
    }
    temp.pop_back();
}

void dijkstra2(int s){
    fill(t, t + maxn, inf);
    t[s] = 0;
    for(int i = 0; i < n; i++) {
        int u = -1, MIN = inf;
        for(int j = 0; j < n; j++) {
            if(vis1[j] == false && t[j] < MIN) {
                u = j;
                MIN = t[j];
            }
        }
        if(u == -1) return;
        vis1[u] = true;
        for(int v = 0; v < n; v++) {
            if(vis1[v] == false && G[u][v] != inf) {
                if(t[u] + T[u][v] < t[v]) {
                    pre1[v].clear();
                    t[v] = t[u] + T[u][v];
                    pre1[v].push_back(u);
                } else if(t[u] + T[u][v] == t[v]) {
                    pre1[v].push_back(u);
                }
            }
        }
    }
}

vector<int> temp1, path1;
int optvalue1 = inf;
void DFS1(int v) {
    if(v == st) {
        temp1.push_back(v);
        int value = temp1.size();
        if(value < optvalue1) {
            optvalue1 = value;
            path1 = temp1;
        }
        temp1.pop_back();
    }
    temp1.push_back(v);
    for(int i = 0; i < pre1[v].size(); i++) {
        DFS1(pre1[v][i]);
    }
    temp1.pop_back();
}

int main(int argc, const char * argv[]) {
    fill(G[0], G[0] + maxn * maxn, inf);
    scanf("%d %d", &n, &m);
    for(int i = 0; i < m; i++) {
        int v1, v2, flag, length, time;
        scanf("%d %d %d %d %d", &v1, &v2, &flag, &length, &time);
        G[v1][v2] = length;
        T[v1][v2] = time;
        if(flag == 0) {
            G[v2][v1] = length;
            T[v2][v1] = time;
        }
    }
    scanf("%d %d", &st, &ed);
    dijkstra1(st);
    DFS(ed);
    dijkstra2(st);
    DFS1(ed);
    bool flag = true;
    if(path.size() != path1.size()) flag = false;
    else {
        for(int i = 0; i < path.size(); i++) {
            if(path[i] != path1[i]) flag = false;
        }
    }
    if(flag == true) {
        printf("Distance = %d; Time = %d: ", d[ed], t[ed]);
        for(int i = path.size() - 1; i >= 0; i--) {
            printf("%d", path[i]);
            if(i > 0) printf(" -> ");
            else printf("\n");
        }
    } else {
        printf("Distance = %d: ", d[ed]);
        for(int i = path.size() - 1; i >= 0; i--) {
            printf("%d", path[i]);
            if(i > 0) printf(" -> ");
            else printf("\n");
        }
        printf("Time = %d: ", t[ed]);
        for(int i = path1.size() - 1; i >= 0; i--) {
            printf("%d", path1[i]);
            if(i > 0) printf(" -> ");
            else printf("\n");
        }
    }
    return 0;
}