AcWing 1497. 树的遍历
原题链接
简单
作者:
PASSIONNNN
,
2024-12-12 20:40:18
,
所有人可见
,
阅读 2
#include <cstring>
#include <iostream>
#include <algorithm>
#include <unordered_map>
using namespace std;
const int N = 40;
int n;
int postorder[N], inorder[N];
unordered_map<int, int> l, r, pos;
int q[N];
int build(int il, int ir, int pl, int pr)
{
int root = postorder[pr];
int k = pos[root];
if (il < k) l[root] = build(il, k - 1, pl, pl + k - 1 - il);//如果当前root有左子树,存入左子树的根节点
if (k < ir) r[root] = build(k + 1, ir, pl + k - 1 - il + 1, pr - 1);
return root;
}
void bfs(int root)
{
int hh = 0, tt = 0;
q[0] = root;
while (hh <= tt)
{
int t = q[hh ++ ];//取出头结点
if (l.count(t)) q[ ++ tt] = l[t];// l 中如果存在键 t,把把t的左子树的根存入队列
if (r.count(t)) q[ ++ tt] = r[t];
}
cout << q[0];
for (int i = 1; i < n; i ++ ) cout << ' ' << q[i];
cout << endl;
}
int main()
{
cin >> n;
for (int i = 0; i < n; i ++ ) cin >> postorder[i];
for (int i = 0; i < n; i ++ )
{
cin >> inorder[i];
pos[inorder[i]] = i;
}
int root = build(0, n - 1, 0, n - 1);
bfs(root);
return 0;
}