B3642 二叉树的遍历

https://www.luogu.com.cn/record/169648364

Luogu/B3642/B3642.cpp

@@ -0,0 +1,61 @@
+#include <iostream>
+#include <algorithm>
+#include <iterator>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+
+int n;
+int lch[N], rch[N];
+int cnt_pre, pre[N],
+    cnt_in, in[N],
+    cnt_post, post[N];
+
+void pre_order(int u) {
+    pre[++cnt_pre] = u;
+
+    if (lch[u]) pre_order(lch[u]);
+    if (rch[u]) pre_order(rch[u]);
+}
+
+void in_order(int u) {
+    if (lch[u]) in_order(lch[u]);
+
+    in[++cnt_in] = u;
+
+    if (rch[u]) in_order(rch[u]);
+}
+
+void post_order(int u) {
+    if (lch[u]) post_order(lch[u]);
+    if (rch[u]) post_order(rch[u]);
+
+    post[++cnt_post] = u;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> lch[i] >> rch[i];
+    }
+
+    pre_order(1);
+    in_order(1);
+    post_order(1);
+
+    std::copy_n(pre + 1, n, std::ostream_iterator<int>(cout, " "));
+    cout << endl;
+    std::copy_n(in + 1, n, std::ostream_iterator<int>(cout, " "));
+    cout << endl;
+    std::copy_n(post + 1, n, std::ostream_iterator<int>(cout, " "));
+    cout << endl;
+
+    return 0;
+}