洛谷 P1346 电车 dijkstra

题目链接：​​https://www.luogu.org/problemnew/show/P1346​​

思路：

这是一道隐藏的最短路问题

把每一个车站看成一个点，将这个车站相连的第一个车站建立一条权为0的边，

对于它所相连的其他车站，建立边权为1的边；

所用算法：

 dijkstra

思路提示博客：

洛谷题解区第一个：​​https://www.luogu.org/problemnew/solution/P1346​​

#include <iostream>
#include<vector>
#include <climits>

using namespace std;
int n, s,t;
bool mark[101];
vector<vector<int> >map[101];
int dis[101];
int maxn = INT_MAX;
vector<int>v;

void search()
{
    mark[s] = 1;
    dis[s] = 0;
    int count = 1;
    while (count<=n)
    {
        int loc = 0;
        int min = maxn;
        for (int i = 1; i <= n; i++)
        {
            if (!mark[i] && dis[i] < min)
            {
                min = dis[i];
                loc = i;
            }
        }
        if (loc == 0)break;
        mark[loc] = 1;
        count++;
        for (int i = 1; i <= n; i++)
        {
            if (!mark[i])
            {
                for (int j = 0; j < map[loc].size(); j++)
                {
                    if (dis[loc] + map[loc][j][1] < dis[map[loc][j][0]])
                    {
                        dis[map[loc][j][0]] = dis[loc] + map[loc][j][1];
                    }
                }
            }
        }
    }
    if (dis[t] != maxn)cout << dis[t] << endl;
    else cout << -1 << endl;

}

int main()
{
    cin >> n >> s >> t;
    for (int i = 1; i <= n; i++)
        dis[i] = maxn;
    for (int i = 1; i <= n; i++)
    {
        int num,a;
        cin >> num;
        for (int j = 0; j < num; j++)
        {
            cin >> a;
            if (j == 0)
            {
                v.push_back(a);
                v.push_back(0);
                map[i].push_back(v);
                v.clear();
                if (i == s)
                {
                    dis[map[i][j][0]] = map[i][j][1];
                }
            }
            else
            {
                v.push_back(a);
                v.push_back(1);
                map[i].push_back(v);
                v.clear();
                if (i == s)
                {
                    dis[map[i][j][0]] = map[i][j][1];
                }
            }
        }
    }
    search();
    return 0;
}