[数据结构与算法]PATA1110_完全二叉树（难度：??）

由于没有孩子节点的值是0，所以我命名的序号是1-N，而不是题目给的0-N；所以最后要减去1。

#include <bits/stdc++.h>
using namespace std;
int n, flag = 0;
bool vis[30];
struct node {
    int val, lc, rc, pos;
}tree[30];
unordered_map<int, int> mp;
void posName (int root, int pos) {
    if (root == 0) return;
    tree[root].pos = pos;
    mp[pos] = root;
    if (pos > n) flag = 1;
    posName(tree[root].lc, pos * 2);
    posName(tree[root].rc, pos * 2 + 1);
}
int main() {
    int root;
    string a, b;
    scanf ("%d", &n);
    for (int i = 1; i <= n; i++) {
        cin >> a >> b;
        if (a[0] != '-') {
            tree[i].lc = stoi(a) + 1;
            vis[stoi(a) + 1] = true;
        }
        else tree[i].lc = 0;
        if (b[0] != '-') {
            tree[i].rc = stoi(b) + 1;
            vis[stoi(b) + 1] = true;
        }
        else tree[i].rc = 0;
    }
    for (int i = 1; i < 30; i++) {
        if (vis[i] == false) {
            root = i;
            break;
        }
    }
    posName(root, 1);
    if (flag == 0) printf ("YES %d", mp[n] - 1);
    else printf ("NO %d", root - 1);
}