HDU-3191 How Many Paths Are There(有向图次短路条数)

题意：指示一个有向图，n个点(0~n-1)，m条边，求出次短路的条数。

思路：Dijkstra修改版(链接)去求。但是有个WA点是在优先队列里当权值相同时，角标需要从小到大排序(暂未解决，难道是有向图的影响?)。

Code：

#include <string.h>#include <cstdio>#include <queue>using namespace std;const int inf = 0x3f3f3f3f;const int maxn = 55;const int maxm = maxn*maxn;struct node1{int v, w, next;} edge[maxm];struct node{int v, w, key;node(int a, int b, int c): v(a), w(b), key(c){}bool operator<(const node k)const{if(w == k.w) return v > k.v;return w > k.w;}};priority_queue<node> q;int n, m, s, t, no;int head[maxn], dis[maxn][2], vis[maxn][2], cnt[maxn][2];inline void init(){no = 0;memset(head, -1, sizeof head);memset(dis, 0x3f, sizeof dis);memset(vis, 0, sizeof vis);memset(cnt, 0, sizeof cnt); while(!q.empty()) q.pop();}inline void add(int u, int v, int w){edge[no].v = v, edge[no].w = w;edge[no].next = head[u]; head[u] = no++;}void DJ(){dis[s][0] = 0, cnt[s][0] = 1;q.push(node(s, 0, 0));while(!q.empty()){node top = q.top(); q.pop();if(vis[top.v][top.key]) continue;vis[top.v][top.key] = 1;int k = head[top.v];while(k != -1){int v = edge[k].v;int tmp = dis[top.v][top.key]+edge[k].w;if(dis[v][0] > tmp){if(dis[v][0] != inf){dis[v][1] = dis[v][0];cnt[v][1] = cnt[v][0];q.push(node(v, dis[v][1], 1));}dis[v][0] = tmp;cnt[v][0] = cnt[top.v][top.key];q.push(node(v, dis[v][0], 0));}else if(dis[v][0] == tmp) cnt[v][0] += cnt[top.v][top.key];else if(dis[v][1] > tmp){dis[v][1] = tmp;cnt[v][1] = cnt[top.v][top.key];q.push(node(v, dis[v][1], 1));}else if(dis[v][1] == tmp) cnt[v][1] += cnt[top.v][top.key];k = edge[k].next;}}}int main(){int u, v, w;while(~scanf("%d %d %d %d", &n, &m, &s, &t)){init();for(int i = 1; i <= m; ++i){scanf("%d %d %d", &u, &v, &w);add(u, v, w);}DJ();printf("%d %d\n", dis[t][1], cnt[t][1]);}return 0;}

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