PAT甲级 1135 - Is It A Red-Black Tree

#include<bits/stdc++.h>
using namespace std;
const int maxn=30+2;
bool flag;
int inOrder[maxn],preOrder[maxn];
bool cmp(int a,int b){
return abs(a)<abs(b);
}
struct node{
int v;
int  b_num;
}tree[1024*1024+1];
void buildTree(int cur,int preL,int preR,int inL,int inR){
if(!flag || preL>preR || inL>inR)return;
int i;
for(i=inL;i<=inR;++i){
if(preOrder[preL]==inOrder[i]){
break;
}
}
tree[cur].v=preOrder[preL];
buildTree(cur<<1,preL+1,preL+i-inL,inL,i-1);
buildTree((cur<<1)|1,preR-inR+i+1,preR,i+1,inR);
if(tree[cur<<1].b_num!=tree[(cur<<1)|1].b_num){
flag=false;
}
if(tree[cur].v<0){//red
if(tree[cur<<1].v<0 || tree[(cur<<1)|1].v<0){
flag=false;
}
tree[cur].b_num=tree[cur<<1].b_num;
}else{//black
tree[cur].b_num=tree[cur<<1].b_num+1;
}
}

int main(){
int k,n;
scanf("%d",&k);
while(k--){
flag=true;
scanf("%d",&n);

for(int i=1;i<=1024*1024;++i){
tree[i].v=0;
tree[i].b_num=0;
}

for(int i=1;i<=n;++i){
scanf("%d",preOrder+i);
inOrder[i]=preOrder[i];
}
sort(inOrder+1,inOrder+1+n,cmp);
buildTree(1,1,n,1,n);
if(tree[1].v<0)flag=false;
if(flag)printf("Yes\n");
else printf("No\n");
}
return 0;
}