SPFA/Dijkstra POJ 3159 Candies

 

题目传送门

题意：n个人发糖果，B 比 A 多 Ｃ的糖果，问最后第n个人比第一个人多多少的糖果

分析：最短路，Dijkstra 优先队列优化可过，SPFA竟然要用栈，队列超时！

 

代码：

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/************************************************ * Author        :Running_Time * Created Time  :2015-9-1 19:18:52 * File Name     :POJ_3159.cpp  ************************************************/   #include <cstdio> #include <algorithm> #include <iostream> #include <sstream> #include <cstring> #include <cmath> #include <string> #include <vector> #include <queue> #include <deque> #include <stack> #include <list> #include <map> #include <set> #include <bitset> #include <cstdlib> #include <ctime> using namespace std;   #define lson l, mid, rt << 1 #define rson mid + 1, r, rt << 1 | 1 typedef long long ll; const int N = 3e4 + 10; const int E = 150000 + 10; const int INF = 0x3f3f3f3f; const int MOD = 1e9 + 7; struct Edge {     int v, w, nex;     Edge (int _v = 0, int _w = 0) : v (_v), w (_w) {}     bool operator < (const Edge &r) const {         return w > r.w;     } }edge[E]; int d[N]; int head[N]; int vis[N]; int cnt[N]; int n, m, e;   void init(void) {     memset (head, -1, sizeof (head));     e = 0; }   void Dijkstra(int s)    {     memset (vis, false, sizeof (vis));     for (int i=1; i<=n; ++i)    d[i] = INF;     d[s] = 0;     priority_queue<Edge> Q;  Q.push (Edge (s, 0));     while (!Q.empty ()) {         int u = Q.top ().v; Q.pop ();         if (vis[u]) continue;         vis[u] = true;         for (int i=head[u]; ~i; i=edge[i].nex)  {             int v = edge[i].v, w = edge[i].w;             if (!vis[v] && d[v] > d[u] + w) {                 d[v] = d[u] + w;    Q.push (Edge (v, d[v]));             }         }     } }   void SPFA(int s)    {     memset (vis, false, sizeof (vis));     memset (d, INF, sizeof (d));     d[s] = 0; vis[s] = true;     stack<int> S;   S.push (s);     while (!S.empty ()) {         int u = S.top (); S.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;  S.push (v);                 }             }         }     } }   void add_edge(int u, int v, int w)  {     edge[e].v = v, edge[e].w = w;     edge[e].nex = head[u];  head[u] = e++; }   int main(void)    {     while (scanf ("%d%d", &n, &m) == 2) {         init ();         for (int u, v, w, i=1; i<=m; ++i)   {             scanf ("%d%d%d", &u, &v, &w);             add_edge (u, v, w);         }         //Dijkstra (1);         SPFA (1);         printf ("%d\n", d[n]);     }       return 0; }