http://hzwer.com/5790.html  代码

http://www.cppblog.com/MatoNo1/archive/2013/03/03/192131.html  //原理讲解  

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,top,root;
int ls[105],rs[105],fa[105],ans[105];
void solve(){
    int x=root;
    while(rs[x]!=-1) x=ls[x];
    int t=ls[x];
    if(t!=-1&&ls[t]==-1&&rs[t]==-1) x=t;
    ans[++top]=x;
    if(x==root) root=ls[root];
    int f=fa[x];
    if(f!=-1) ls[f]=ls[x],fa[ls[f]]=f;
    while(f!=-1) swap(ls[f],rs[f]),f=fa[f];
}
int main(){
    fa[0]=-1;
    memset(ls,-1,sizeof(ls));
    memset(rs,-1,sizeof(rs));
    scanf("%d",&n);
    for(int i=1;i<=n;++i) {
        int x;scanf("%d",&x);
        if(x<100) ls[x]=i,fa[i]=x;
        else rs[x-100]=i,fa[i]=x-100;
    }
    for(int i=1;i<=n+1;++i)
        solve();
    while(top)  printf("%d ",ans[top--]);
}

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