POJ 1095 Trees Made to Order(卡特兰数列)

题目链接

中间计算的各种细节。有的细节没处理好，就wa了。。。主要思路就是根据卡特兰数列的：

h(n)= h(0)*h(n-1)+h(1)*h(n-2) + ... + h(n-1)h(0) (n>=2)

 #include <cstdio>
 #include <string>
 #include <cstring>
 #include <queue>
 #include <map>
 #include <iostream>
 #include <algorithm>
 using namespace std;
 #define LL __int64
 LL ctl[];
 LL sum[];
 struct node
 {
     int l,r;
 }tree[];
 int t;
 void build(LL n,int rt)
 {
     int i,pos;
     if(n == ||n == )
     {
         return ;
     }
     for(i = ;i <= ;i ++)
     {
         if(sum[i] >= n)
         break;
     }
     pos = i;
     n -= sum[pos-];
     for(i = ;i <= pos-;i ++)
     {
         if(n <= ctl[i]*ctl[pos--i])
         break;
         n -= ctl[i]*ctl[pos--i];
     }
     if(i != )
     {
         tree[rt].l = t ++;
         if(n%ctl[pos--i] != )
         build(sum[i-]+n/ctl[pos--i]+,t-);
         else
         build(sum[i-]+n/ctl[pos--i],t-);
     }
     if(i != pos-)
     {
         tree[rt].r = t ++;
         if(n%ctl[pos--i] == )
         build(sum[pos--i]+ctl[pos--i],t-);
         else
         build(sum[pos--i]+n%ctl[pos--i],t-);
     }
 }
 void show(int x)
 {
     if(x == -)
     return ;
     if(tree[x].l != -)
     printf("(");
     show(tree[x].l);
     if(tree[x].l != -)
     printf(")");
     printf("X");
     if(tree[x].r != -)
     printf("(");
     show(tree[x].r);
     if(tree[x].r != -)
     printf(")");
 
 }
 int main()
 {
     int i;
     LL n;
     ctl[] = ;
     ctl[] = ;
     sum[] = ;
     for(i = ;i <= ;i ++)
     {
         ctl[i] = ctl[i-]*(*i-)/(i+);
         sum[i] = sum[i-] + ctl[i];
     }
     while(cin>>n)
     {
         if(n == ) break;
         t = ;
         for(i = ;i <= ;i ++)
         tree[i].l = tree[i].r = -;
         build(n,);
         show();
         printf("\n");
     }
     return ;
 }