POJ1988--cube stacking(2007-04-18 17:01)

 

对并查集的扩展.看了下解题报告,总算有想法了.

sum[i]记录根结点i下面的结点数(包括自己)和up[i]记录在某结点i上面的结点数.则在一结点m之下的结点数为sum[findpar(m)]-up[m]-1   (findpar查找根结点)

在uni和findpar过程中更新sum和up的内容.(蓝色部分)

1. #include "stdio.h"
3. const int max_node=30005;
5. int par[max_node+1];
6. int up[max_node+1];
7. int sum[max_node+1];
8. int add;
10. int findpar(int num){
11.          int top;
12.          if(par[num]!=num){
13.                  top=findpar(par[num]);
14.                 if(top!=par[num]){
15.                          up[num]+=add;
16.                  }
17.                  add=up[num];
18.                  par[num]=top;
19.                  return top;
20.          }
21.          return num;
22. }
24. void uni(int a,int b){
25.          a=findpar(a);
26.          b=findpar(b);
27.          par[b]=a;
28.         up[b]=sum[a];
29.          sum[a]+=sum[b];
30. }
31.         
33. int main()
34. {
35. //         freopen("1.in","r",stdin);
36.          int p;
37.          scanf("%d",&p);
38.          while(getchar()!='/n');
39.          int s,d;
40.          char c;
41.          int i;
42.          for(i=0;i< =max_node;++i){
43.                  par[i]=i;
44.                  up[i]=0;
45.                  sum[i]=1;
46.          }
47.          while(p-->0){
48.                  c=getchar();
49.                  if(c=='M'){
50.                          scanf("%d %d",&s,&d);
51.                          while(getchar()!='/n');
52.                          uni(s,d);
53.                  }
54.                  else{
55.                          scanf("%d",&d);
56.                          while(getchar()!='/n');
57.                          printf("%d/n",sum[findpar(d)]-up[d]-1);
58.                  }
59.          }
60.          return 0;
61. }