代码丢这儿了...

#include <bits/stdc++.h>
using namespace std;
struct node {
    char v = 0;
    node *l = nullptr, *r = nullptr;
};
node *in_nodes[10];
node *pos_nodes[10];

node *buildTree(int inStart, int inEnd, int posStart, int posEnd) {
    if (inStart >= inEnd || posStart >= posEnd)return nullptr;
    node *root = pos_nodes[posEnd - 1];
    int index = inStart;
    while (in_nodes[index]->v != root->v)index++;

    root->l = buildTree(inStart, index, posStart, posStart + index - inStart);
    root->r = buildTree(index + 1, inEnd, posStart + index - inStart, posEnd - 1);
    return root;
}

void prePrint(node *root) {
    if (root == nullptr)return;
    cout << root->v;
    prePrint(root->l);
    prePrint(root->r);
}

int main() {
    char c;
    int len = 0;
    node *tmp_nodes[256];
    while ((c = getchar()) != '\n') {
        node *tmp = new node();
        tmp->v = c;
        in_nodes[len++] = tmp_nodes[c] = tmp;
    }
    len = 0;
    while ((c = getchar()) != '\n') {
        pos_nodes[len++] = tmp_nodes[c];
    }
    prePrint(buildTree(0, len, 0, len));
    return 0;
}

把cout << root->v;改成putchar(root->v);就好了。是评测机的锅嘛？