1016: [JSOI2008]最小生成树计数

来源：互联网发布：log4j打印sql日志编辑：程序博客网时间：2024/06/11 03:17

不知为何使用路径压缩的并查集会WA。

#include<algorithm>#include<iostream>#include<cstdio>#define inf 0x7fffffffusing namespace std;inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}struct edge{int x,y,v;}e[1001];struct data{int l,r,v;}a[1001];int n,m,cnt,tot,ans=1,sum,fa[101];inline int find(int x){return fa[x]==x?x:find(fa[x]);}inline bool cmp(edge a,edge b){return a.v<b.v;}void dfs(int x,int now,int k){if(now==a[x].r+1){if(k==a[x].v)sum++;return;}int p=find(e[now].x),q=find(e[now].y);if(p!=q){fa[p]=q;dfs(x,now+1,k+1);fa[p]=p;fa[q]=q;}dfs(x,now+1,k);}int main(){n=read();m=read();for(int i=1;i<=m;i++)e[i]=(edge){read(),read(),read()};for(int i=1;i<=n;i++)fa[i]=i;sort(e+1,e+m+1,cmp);for(int i=1;i<=m;i++){if(e[i].v!=e[i-1].v){a[++cnt].l=i;a[cnt-1].r=i-1;}int p=find(e[i].x),q=find(e[i].y);if(p!=q){fa[p]=q;a[cnt].v++;tot++;}}a[cnt].r=m;if(tot!=n-1){printf("0");return 0;}for(int i=1;i<=n;i++)fa[i]=i;for(int i=1;i<=cnt;i++){sum=0;dfs(i,a[i].l,0);ans=(ans*sum)%31011;for(int j=a[i].l;j<=a[i].r;j++){int p=find(e[j].x),q=find(e[j].y);if(p!=q)fa[p]=q;}}printf("%d",ans);}

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