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 (≤) 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;
const int maxn=1010;
#define  inf  0x3fffffff
struct node{
    int lchild=-1;
    int rchild=-1;
}node[maxn];
int dex=1;
int flag[maxn];
int maxdex=-1;
int ans=-1;
void dfs(int root,int index){
    if(index>maxdex){
        maxdex=index;
        ans=root;
    }
    if(node[root].lchild!=-1){
        dfs(node[root].lchild,index*2);
    }
    if(node[root].rchild!=-1){
        dfs(node[root].rchild,index*2+1);
    }
}
int main(){
    int n;
    scanf("%d",&n);
//    char a,b;
    string a,b;
    for(int i=0;i<n;i++){
        cin>>a>>b;//a和b可能是两位数，故不能用char存储
        if(a=="-"){
            node[i].lchild=-1;
        }
        else{
            int sum=0;
            for(int j=0;j<a.length();j++){
                sum=sum*10+(a[j]-'0');
            }
            node[i].lchild=sum;
            flag[node[i].lchild]=1;
        }
        if(b=="-"){
            node[i].rchild=-1;
        }
        else{
            int sum=0;
            for(int j=0;j<b.length();j++){
                sum=sum*10+(b[j]-'0');
            }
            node[i].rchild=sum;
            flag[node[i].rchild]=1;
        }
    }
    int root;
    for(int i=0;i<n;i++){
        if(flag[i]!=1){
            root=i;
            break;
        }
    }
    dfs(root,1);
    
    if(maxdex>n){
        printf("NO %d\n",root);
    }
    else{
        printf("YES %d\n",ans);
    }
    return 0;
}