2019冬季PAT甲级第四题

 #define HAVE_STRUCT_TIMESPEC
 #include<bits/stdc++.h>
 using namespace std;
 typedef struct node{
     int data;
     node *lchild,*rchild;
 }tree;
 int a[];
 tree *build(int l,int r){
     if(l>r)
         return NULL;
     int mn=1e9+,pos=;
     for(int i=l;i<=r;++i)
         if(a[i]<mn)
             mn=a[i],pos=i;
     tree *temp=new tree();
     temp->data=mn;
     temp->lchild=build(l,pos-);
     temp->rchild=build(pos+,r);
     return temp;
 }
 int main(){
     ios::sync_with_stdio(false);
     cin.tie(NULL);
     cout.tie(NULL);
     int n;
     cin>>n;
     for(int i=;i<=n;++i)
         cin>>a[i];
     tree *temp=build(,n);
     queue<tree *>q;
     q.push(temp);
     int ans[]={};
     int cnt=;
     while(!q.empty()){
         tree *now=q.front();
         q.pop();
         ans[++cnt]=now->data;
         if(now->lchild)
             q.push(now->lchild);
         if(now->rchild)
             q.push(now->rchild);
     }
     for(int i=;i<=cnt;++i){
         if(i>)
             cout<<" ";
         cout<<ans[i];
     }
     return ;
 }