1003 Emergency

1003 Emergency

java代码提交注意点

1. 类名改为Main

2. 不要有package

题目注意点

1. 考虑出发城市和目的城市相同！！！

总体思路

1. 用迪杰斯特拉算法求出发城市到目的城市之间的最短距离(不需要走完全部的过程，一旦求出两者之间的最短距离就可以break)
2. 使用递归遍历所有路径(条件：路径和必须<=min<出发，目的>，否则不递归)，递归的出口是顶点为终点时候

java代码

import java.util.HashSet;
import java.util.Scanner;

public class A1003 {

    int cityNum;
    int[][] map; // 地图
    int[] teamNum;
    int startCity;
    int endCity;
    int value; //最短路径
    int ways = 0; //最短路数
    int maxTeam = 0; //最大团队数

    A1003(int length, int startCity, int endCity) {
        this.cityNum = length;
        this.startCity = startCity;
        this.endCity = endCity;
        teamNum = new int[length];
        map = new int[length][length];
        for (int i = 0; i < length; i++) {
            for (int j = 0; j < length; j++) {
                map[i][j] = 0;
            }
        }
    }

    void getMinDistance() {
        int startPoint = startCity;
        int[] path = new int[cityNum];
        int[] values = new int[cityNum];
        int[] help = new int[cityNum];
        for (int i = 0; i < cityNum; i++) {
            values[i] = Integer.MAX_VALUE;
            help[i] = 0;
        }
        path[startPoint] = startPoint;
        help[startPoint] = 1;
        values[startPoint] = 0;
        while (true) {
            for (int i = 0; i < cityNum; i++) {
                if (map[startPoint][i] != 0) {
                    if (map[startPoint][i] + values[startPoint] < values[i]) {
                        values[i] = map[startPoint][i] + values[startPoint];
                        path[i] = startPoint;
                    }
                }
            }
            int min = Integer.MAX_VALUE;
            int index = -1;
            for (int i = 0; i < cityNum; i++) {
                if (help[i] != 1) {
                    if (values[i] < min) {
                        min = values[i];
                        index = i;
                    }
                }
            }
            if (index == endCity) {
                this.value = min;
                break;
            }
            help[index] = 1;
            startPoint = index;
        }
    }

    void dfs(int index, int teams, int values, HashSet<Integer> set) {
        if (index == this.endCity) {
            if (teams > this.maxTeam) {
                maxTeam = teams;
            }
            this.ways++;
            return;
        }
        for (int i = 0; i < this.cityNum; i++) {
            if (this.map[index][i] != 0 && !set.contains(i)) {
                if (values + this.map[index][i] <= this.value) {
                    HashSet<Integer> set1 = (HashSet<Integer>) set.clone();
                    set1.add(i);
                    dfs(i, teams + this.teamNum[i], values + this.map[index][i], set1);
                }
            }
        }
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int cityNum = in.nextInt();
        int roadNum = in.nextInt();
        A1003 a1003 = new A1003(cityNum, in.nextInt(), in.nextInt());
        for(int i=0;i<cityNum;i++){
            a1003.teamNum[i] = in.nextInt();
        }
        for(int i=0;i<roadNum;i++){
            int row = in.nextInt();
            int col = in.nextInt();
            int value = in.nextInt();
            a1003.map[row][col] = value;
            a1003.map[col][row] = value;
        }
        if(a1003.startCity == a1003.endCity) {
            System.out.println(1 + " " + a1003.teamNum[a1003.startCity]);
        }else {
            a1003.getMinDistance();
            HashSet<Integer> set = new HashSet<Integer>();
            set.add(a1003.startCity);
            a1003.dfs(a1003.startCity, a1003.teamNum[a1003.startCity], 0, set);
            System.out.println(a1003.ways + " " + a1003.maxTeam);
        }
        in.close();
    }
}

转载于:https://www.cnblogs.com/d-i-p/p/10618007.html