• Gym


    题意: 给n个点m条边及每条边所花费的时间,经过给定的p个点时会停留k秒,要求在t秒内从1号点走到n号点,若可以走到输出最短时间,若不行输出-1.。

    题解:读取边时,将每个点停留的时间加到以其为终点的边的花费上。比如边1 2 10,且2是给定的停留点(设停留5s),则读入这条边时按 1 2 15 读入,然后正常dijkstra即可。

    坑点:单位有分有秒/有向边/参数貌似很多。由于一直找不到wa在哪里,先是怀疑爆int,然后把那个多余的map简化成了bool数组,又把输出时的if,else优化了一下,(只是把代码弄得短一些,然并卵)最后怀疑邻接链表有问题,全部改成链式前向星ORZ,依然并卵。又怀疑dijkstra要加vis数组,依然并卵。最后改priority_queue,先发现prioirity_queue<int,vector<int>,greater<int> > 报错,只能用了一个point结构体重载+-,然而并没有什么卵用!!最后发现自己多写了一行T*=60 Orz

    ac代码:

    #include<iostream>
    #include<vector>
    #include<queue>
    #include<map>
    using namespace std;
    typedef long long ll;
    const ll maxn = 1e5 + 5;
    ll n, m, k, p;
    long long T;
    vector< pair<ll, ll> > E[maxn];
    ll d[maxn];
    map<ll, ll> pine;
    void init() {
        for (ll i = 0; i <maxn; i++) E[i].clear(), d[i] = 2e18;
    }
    int  main()
    {
    
        while (cin >> n >> m >> T >> k >> p) {
            //T *= 60;
            for (ll i = 0; i<p; i++) {
                ll x; cin >> x; pine[x]++;
            }
    
            init();
            for (ll i = 0; i < m; i++) {
                ll x, y;
                long long z;
                cin >> x >> y >> z;
                z *= 60;
    
                if (pine.count(y))
                    E[x].push_back(make_pair(y, z + k));
                else E[x].push_back(make_pair(y, z));
            }
    
            ll s = 1, t = n;
            priority_queue<pair<ll, ll> > Q;
            d[s] = 0; Q.push(make_pair(-d[s], s));
            while (!Q.empty()) {
                ll now = Q.top().second;
                Q.pop();
    
                for (ll i = 0; i < E[now].size(); i++)
                {
                    ll v = E[now][i].first;
                    if (d[v] > d[now] + E[now][i].second) {
                        d[v] = d[now] + E[now][i].second;
    
                        Q.push(make_pair(-d[v], v));
                    }
                }
            }
            
            if (d[t] == 2e18 || d[t] > T * 60)cout << -1 << endl;
            else cout << d[t] << endl;
    
        }
    }

    一度改得面目全非:

    #define _CRT_SECURE_NO_WARNINGS
    #include<stdio.h>
    #include<queue>
    #include<string.h>
    using namespace std;
    const long long maxn = 100005;
    typedef long long ll;
    ll n, m, k, p,T;
    ll pine[maxn];
    ll head[maxn], now,dis[maxn],vis[maxn];
    struct edge {
        ll to, next, val;
    }e[2*maxn];
    void addedge(ll x, ll y, ll z) {
        e[++now].to = y, e[now].val = z, e[now].next = head[x], head[x] = now;
    }
    struct point {
        ll val, id;
        point(ll id, ll val) :id(id), val(val) {}
        bool operator <(const point &x) const {
            return val > x.val;
        }
    };
    void dij(ll s) {
        priority_queue<point>Q;
        Q.push(point(s, 0));
        vis[s] = 1;
        dis[s] = 0;
        while (!Q.empty()) {
            ll cur = Q.top().id;
            Q.pop();
            vis[cur] = 1;
            for (ll i = head[cur]; i != -1; i = e[i].next) {
                ll id = e[i].to;
                if (!vis[id] && (dis[cur] + e[i].val < dis[id] || dis[id] == -1)) {
                    dis[id] = dis[cur] + e[i].val;
                    Q.push(point(id, dis[id]));
                }
            }
        }
    
    }
    int main(){
    
        scanf("%lld%lld%lld%lld%lld", &n, &m, &T, &k, &p);
        memset(head, -1, sizeof(head));
        memset(dis, -1, sizeof(dis));
        //T *= 60;
        for (ll i = 0; i<p; i++) {
            ll x; scanf("%lld", &x); pine[x] = 1;
        }
        for (ll i = 0; i < m; i++) {
            ll x, y;
            long long z;
            scanf("%lld%lld%lld", &x, &y, &z);
            z *= 60;
            addedge(x, y, k*pine[y] + z);
        }
        dij(1);
        if (dis[n] <= T * 60)    printf("%lld", dis[n]);
        else printf("-1");
    }



    成功的路并不拥挤,因为大部分人都在颓(笑)
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  • 原文地址:https://www.cnblogs.com/SuuT/p/8530326.html
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