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
果然 ! 数组是做完美或完全二叉树的神器!!
code
#pragma warning(disable:4996)
#include <iostream>
#include <string>
using namespace std;
int tree[22][2];
int treearr[22];
bool vis[22];
void init();
int tran(string s);
bool iscomplete(int idex, int pos);
int n;
int main() {
init();
cin >> n;
string a, b;
for (int i = 0; i < n; ++i) {
cin >> a >> b;
if (a != "-") {
tree[i][0] = tran(a);
vis[tree[i][0]] = 1;
}
if (b != "-") {
tree[i][1] = tran(b);
vis[tree[i][1]] = 1;
}
}
int root;
for (int i = 0; i < n; ++i) {
if (vis[i] == 0) {
root = i;
break;
}
}
if (iscomplete(root,1)) {
cout << "YES" << ' ' << treearr[n] << endl;
}
else {
cout << "NO" << ' ' << root << endl;
}
system("pause");
return 0;
}
void init() {
for (int i = 0; i < 22; ++i) {
tree[i][0] = -1;
tree[i][1] = -1;
}
}
int tran(string s) {
int res = 0;
for (int i = 0; i < s.size(); ++i) {
res *= 10;
res += (s[i] - '0');
}
return res;
}
bool iscomplete(int idex, int pos) {
if (idex == -1) return 1;
if (pos > n) return 0;
if (iscomplete(tree[idex][0], pos * 2) == 0) return 0;
if (iscomplete(tree[idex][1], pos * 2 + 1) == 0) return 0;
treearr[pos] = idex;
return 1;
}