03-树2 List Leaves

用数组模拟出二叉树，并采用并查集的方法来找出树根。

#include <iostream>
#include <algorithm>
#include <queue>
#define Null -1
#define pTree int
using namespace std;
struct TNode{
    int lc, rc;
};
TNode node[10];
int parent[10];
pTree Create()
{
    int n;
    cin >> n;
    for (int i = 0; i != n; ++i)
        parent[i] = i;
    char lc, rc;
    for (int i = 0; i != n; ++i)
    {
        cin >> lc >> rc;
        if (isdigit(lc))
        {
            node[i].lc = lc - '0';
            parent[lc - '0'] = i;
        }
        else
            node[i].lc = Null;
        if (isdigit(rc))
        {
            node[i].rc = rc - '0';
            parent[rc - '0'] = i;
        }
        else
            node[i].rc = Null;
    }
    pTree root = Null;
    for (int i = 0; i != n; ++i)
        if (parent[i] == i)
        {
            root = i;
            break;
        }
    return root;
}

int _count = 0;

void traversal_in_order(pTree a)
{
    queue<pTree> q;

    q.push(a);
    while (!q.empty())
    {
        int a = q.front();
        q.pop();

        if (node[a].lc == Null && node[a].rc == Null)
        {
            if (_count != 0)
                cout << ' ';
            ++_count;
            cout << a;
            continue;
        }
        if (node[a].lc != Null)
            q.push(node[a].lc);
        if (node[a].rc != Null)
            q.push(node[a].rc);
    }
}

int main(void)
{
    ios::sync_with_stdio(false);
    pTree tree = Create();
    traversal_in_order(tree);
    return 0;
}