1110 Complete Binary Tree (25 分)
Given a tree, you are supposed to tell if it is a complete binary tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤20) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N−1. Then N lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a -
will be put at the position. Any pair of children are separated by a space.
Output Specification:
For each case, print in one line YES
and the index of the last node if the tree is a complete binary tree, or NO
and the index of the root if not. There must be exactly one space separating the word and the number.
Sample Input 1:
9
7 8
- -
- -
- -
0 1
2 3
4 5
- -
- -
Sample Output 1:
YES 8
Sample Input 2:
8
- -
4 5
0 6
- -
2 3
- 7
- -
- -
Sample Output 2:
NO 1
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
struct node{
int l,r;
}p[100];
bool mp[100];
int get_num(char s[]){
int num=0;
int len=strlen(s);
for(int i=0;i<len;i++) num=num*10+(s[i]-'0');
return num;
}
void get_son(int fa,char ls[],char rs[]){
if(ls[0]=='-') p[fa].l=-1;
else{
int lson=get_num(ls);
p[fa].l=lson;
mp[lson]=true;
}
if(rs[0]=='-') p[fa].r=-1;
else{
int rson=get_num(rs);
p[fa].r=rson;
mp[rson]=true;
}
}
int mx=-1,ans;
void dfs(int fa,int index){
if(index>mx) mx=index,ans=fa;
if(p[fa].l!=-1) dfs(p[fa].l,index<<1);
if(p[fa].r!=-1) dfs(p[fa].r,index<<1|1);
}
int main(){
int n;
scanf("%d",&n);
for(int i=0;i<n;i++){
char ls[5],rs[5];
scanf("%s%s",ls,rs);
get_son(i,ls,rs);
}
int root=-1;
for(int i=0;i<n;i++){
if(!mp[i]){
root=i;
break;
}
}
dfs(root,1);
if(mx==n) printf("YES %d\n",ans);
else printf("NO %d\n",root);
return 0;
}