标签：file clu com 表示 开始 lib 层序遍历 ber fir
Given a tree, you are supposed to tell if it is a complete binary tree.
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.
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.
9 7 8 - - - - - - 0 1 2 3 4 5 - - - -
YES 8
8 - - 4 5 0 6 - - 2 3 - 7 - - - -
NO 1
解题思路：
这道题开始提交，有三个点通过不了，都显示段错误，想了半天，不应该段错误啊，原来是最开始输入，我用的是char输入，如果节点编号 >= 10那么char读不出来。应该用strng 输入，然后判断是否是" - "，是的话存为-1，否则正常存。
还有就是，判断完全二叉树，用层序遍历，如果前n个遍历序列没有出现-1，说明是完全二叉树，如果前n个序列出现了-1，则表示不是完全二叉树。代码如下
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
int tree[30];
int find(int x){ //寻找节点的根节点
if(tree[x] == x){
return x;
}
return find(tree[x]);
}
int main(){
freopen("C:\\Users\\zzloyxt\\Desktop\\1.txt","r",stdin);
int n;
scanf("%d",&n);
for(int i=0;i<n;i++){ //存放每个下标节点的父亲节点。
tree[i] = i;
}
int left[n];
int right[n];
char a[3],b[3];
for(int i=0;i<n;i++){
scanf("%s %s",a,b);
if(strcmp(a,"-") ==0){
left[i] = -1;
}else{
int a_int = 0;
sscanf(a,"%d",&a_int);
left[i] = a_int;
tree[a_int] = i;
}
if(strcmp(b,"-") ==0){
right[i] = -1;
}else{
int b_int = 0;
sscanf(b,"%d",&b_int); //将字符串转成整数。
right[i] = b_int;
tree[b_int] = i;
}
}
int root = find(0);
int shu[100] = {0}; //存放层序遍历序列
int index = 0;
queue<int> Q;
Q.push(root);
while(!Q.empty()){
int x = Q.front();
Q.pop();
shu[index++] = x;
if(x != -1){
Q.push(left[x]);
Q.push(right[x]);
}
}
int flag = 0;
for(int i=0;i<n;i++){
if(shu[i] < 0){
flag = 1;
break;
}
}
if(flag ==0){
printf("YES %d\n",shu[n-1]);
}else{
printf("NO %d\n",root);
}
return 0;
}
1110 Complete Binary Tree (25分) 判断一棵二插树是否是完全二叉树
标签：file clu com 表示 开始 lib 层序遍历 ber fir
原文地址：https://www.cnblogs.com/zzlback/p/12422430.html
