SPFA(建图) HDOJ 4725 The Shortest Path in Nya Graph

题目传送门

题意:有两种路径,每个点会分别在某一层,层相邻之间权值c.还有直接两点传送,花费w.问1到n的最短距离.

分析:1~n正常建边.然后n + a[i]表示i点在第a[i]层.然后再优化些就不会超时了.

#include <cstdio>

#include <algorithm>

#include <cstring>

#include <queue>

using namespace std;

const int N = 2e5 + 5;

const int E = N * 20;

const int INF = 0x3f3f3f3f;

struct Edge	{

	int v, w, nex;

	Edge() {}

	Edge(int v, int w, int nex) : v (v), w (w), nex (nex) {}

}edge[E];

int head[N];

int d[N];

int a[N];

bool vv[N];

bool vis[N];

int n, m, e;

void init(void)	{

	memset (head, -1, sizeof (head));

	memset (vv, false, sizeof (vv));

	e = 0;

}

void add_edge(int u, int v, int w)	{

	edge[e] = Edge (v, w, head[u]);

	head[u] = e++;

}

void SPFA(int s)	{

	memset (vis, false, sizeof (vis));

	memset (d, INF, sizeof (d));

	d[s] = 0;	vis[s] = true;

	queue<int> que;	que.push (s);

	while (!que.empty ())	{

		int u = que.front ();	que.pop ();

		vis[u] = false;

		for (int i=head[u]; ~i; i=edge[i].nex)	{

			int v = edge[i].v, w = edge[i].w;

			if (d[v] > d[u] + w)	{

				d[v] = d[u] + w;

				if (!vis[v])	{

					vis[v] = true;	que.push (v);

				}

			}

		}

	}

}

int main(void)	{

	int T, cas = 0;	scanf ("%d", &T);

	while (T--)	{

		init ();

		int c;	scanf ("%d%d%d", &n, &m, &c);

		for (int i=1; i<=n; ++i)	{

			scanf ("%d", &a[i]);

			vv[a[i]] = true;

		}

		for (int i=1; i<n; ++i)	{

			if (vv[i] && vv[i+1])	{

				add_edge (n+i, n+i+1, c);

				add_edge (n+i+1, n+i, c);

			}

		}

		for (int i=1; i<=n; ++i)	{

			add_edge (n+a[i], i, 0);

			if (a[i] > 1)	add_edge (i, n+a[i]-1, c);

			if (a[i] < n)	add_edge (i, n+a[i]+1, c);

		}

		for (int u, v, w, i=1; i<=m; ++i)	{

			scanf ("%d%d%d", &u, &v, &w);

			add_edge (u, v, w);	add_edge (v, u, w);

		}

		SPFA (1);

		printf ("Case #%d: %d\n", ++cas, d[n] == INF ? -1 : d[n]);

	}

	return 0;

}