[UVa] 10801 Lift Hopping.cpp

#include <iostream>
#include <sstream>
#include <queue>
using namespace std;
#define Inf 99999999

int main()
{
    ios::sync_with_stdio(false);
    int n, k;
    int T[6];
    int Floor[100];
    int Weight[100][100];
    int Dis[100];
    while (cin >> n >> k)
    {
        for (int i = 1; i <= n; ++i)
            cin >> T[i];

        for (int i = 0; i < 100; ++i) {
            Dis[i] = Inf;
            for (int j = 0; j < 100; ++j)
                Weight[i][j] = Inf;
        }

        cin.ignore();
        for (int i = 1; i <= n; ++i) {
            string str;
            getline(cin, str);
            stringstream ss(str);
            int Count = 0;
            while (ss >> Floor[Count]) ++Count;

            for (int x = 0; x < Count; ++x)
                for (int y = x + 1; y < Count; ++y) {
                    int f1 = Floor[x], f2 = Floor[y];
                    if ((f2-f1)*T[i] < Weight[f1][f2])
                        Weight[f1][f2] = Weight[f2][f1] = (f2-f1)*T[i];
                }
        }

        queue<int> Q;
        int inQueue[101] = {0};
        Dis[0] = 0;
        inQueue[0] = true;
        Q.push(0);
        while (!Q.empty()) {
            int now = Q.front();
            inQueue[now] = false;
            Q.pop();

            for (int nxt = 0; nxt < 100; ++nxt) {
                if (Dis[now] + Weight[now][nxt] + 60 < Dis[nxt]) {
                    Dis[nxt] = Dis[now] + Weight[now][nxt] + 60;
                    if (!inQueue[nxt]) {
                        Q.push(nxt);
                        inQueue[nxt] = true;
                    }
                }
            }
        }
        if (k == 0) cout << 0 << endl;  // 不加這行答案會是-60
        else if (Dis[k] == Inf) cout << "IMPOSSIBLE" << endl;
        else cout << Dis[k] - 60 << endl;
        // SPFA把起點也當成有轉換電梯了 所以答案要減掉60
    }
}

why you add a 60 in the 53 number line if (Dis[now] + Weight[now][nxt] + 60 < Dis[nxt]) ..?? I dont get it cuz every time it adds additional 60 as Dis was set to Inf .. :/