hdu 4725 The Shortest Path in Nya Graph (加虛擬點建圖+最短路）

我因爲加了點變成一個2n個點，一開始dij沒傳入2n，沒過，後來看了半天，原來是初始化時候沒傳入2*n，枯了。

思路：
把每一層也當做一個點，所以這樣一共就有2n個點，假設x點在y層，我的思路y層的點標爲(y+n),然後爲x到(y+n-1)和(y+n+1) [ps：如果在[n+1,2n]範圍內的話]加上一條權值爲c的單向邊，爲(y+n)到x加上一條權值爲0的單向邊，當然我看別人做法有把每一層分成一個入點和一個出點的，也一樣。
注意建圖權值大小和邊是單向還是雙向要搞清。

#include <bits/stdc++.h>

#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define forn(i, n) for (int i = 0; i < (int)(n); ++i)
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)
#define ford(i, a, b) for (int i = (int)(a); i >= (int)b; --i)
#define fore(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
#define rep(i, l, r) for (int i = (l); i <= (r); i++)
#define per(i, r, l) for (int i = (r); i >= (l); i--)
#define ms(x, y) memset(x, y, sizeof(x))
#define SZ(x) ((int)(x).size())

using namespace std;

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef long long i64;
typedef vector<i64> vi64;
typedef vector<vi64> vvi64;
typedef pair<i64, i64> pi64;
typedef double ld;

template<class T> bool uin(T &a, T b) { return a > b ? (a = b, true) : false; }
template<class T> bool uax(T &a, T b) { return a < b ? (a = b, true) : false; }

const int maxn = 2*(int)1e5+100; //點數
const i64 INF = 0x3f3f3f3f3f3f3f3fLL;
struct node {
    int id;
    i64 w;
    node(){}
    node(int a, int b) : id(a), w(b) {}
    friend bool operator < (node a, node b) {return a.w > b.w;}
};
vector<node> G[maxn];
bool vis[maxn];
i64 dis[maxn];

void dij(int s, int n) {
    priority_queue<node> q;
    node cur;
    ms(vis, 0);
    for (int i = 1; i <= n; ++i) dis[i] = INF;
    dis[s] = 0;
    q.push(node(s, dis[s]));
    while (!q.empty()) {
        cur = q.top();
        q.pop();
        if (vis[cur.id]) continue;
        vis[cur.id] = 1;
        for (node to : G[cur.id]) {
            if (!vis[to.id] && dis[to.id] > dis[cur.id]+to.w) {
                dis[to.id] = dis[cur.id]+to.w;
                q.push(node(to.id, dis[to.id]));
            }
        }
    }
}
void init(int n) {
    for (int i = 0; i <= n; ++i) G[i].clear();
}
int tc, n, m, c, l[maxn];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.precision(10);
    cout << fixed;
#ifdef LOCAL_DEFINE
    freopen("input.txt", "r", stdin);
#endif

    cin >> tc;
    int kase = 1;
    while (tc--) {
        cin >> n >> m >> c;
        init(2*n);
        for1(i, n) {
            cin >> l[i];
            int stan = l[i]+n; //對應的層點
            if (stan-1 > n) {
                G[i].eb(node(stan-1, c));
            }
            if (stan+1 <= 2*n) {
                G[i].eb(node(stan+1, c));
            }
            G[stan].eb(node(i, 0));
        }
        forn(i, m) {
            int u, v, val;
            cin >> u >> v >> val;
            G[u].eb(node(v, val));
            G[v].eb(node(u, val));
        }
        dij(1, 2*n);
        cout << "Case #" << kase++ << ": ";
        if (dis[n] == INF) cout << -1 << '\n';
        else cout << dis[n] << '\n';
    }

#ifdef LOCAL_DEFINE
    cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
    return 0;
}