1110 Complete Binary Tree （25 分）(搜索)

2024-04-06 00:12:11

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

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代码：

#include<bits/stdc++.h>
using namespace std;
struct Node{int data;int l,r;
}gg[25];
int flag = 0, maxn = -1,ans;
void DFS(int root, int id)
{if(id > maxn){maxn = id;ans = root;}if(gg[root].l != -1)DFS(gg[root].l, id * 2);if(gg[root].r != -1)DFS(gg[root].r, id * 2 + 1);return ;
}
int main()
{int n;char s1[5],s2[5];int b[22] = {0};scanf("%d", &n);for(int i = 0 ;i < n; i++){scanf("%s %s",s1,s2);if(s1[0] == '-')gg[i].l = -1;else {int data = 0, now = 0;while(s1[now] != '\0')data = data * 10 + s1[now++]-'0'; b[data] = 1;gg[i].l = data;}if(s2[0] == '-')gg[i].r = -1;else {int data = 0, now = 0;while(s2[now] != '\0')data = data * 10 + s2[now++]-'0'; b[data] = 1;gg[i].r = data;}gg[i].data = i;}int root = 0;for(int i = 0; i < n; i ++){if(b[i] == 0){root = i;break;} }DFS(root, 1);if(maxn == n)printf("YES %d\n",ans);else printf("NO %d\n",root);return 0;
}

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