我在洛谷上面远程提交到UVA的数据通过了，但是在POJ莫名不知道为什么没有通过，请大佬帮忙看看哪里写错了呀555

代码：
#include <iostream>
#include <cstring>
#include <string>
#include <stack>
#include <cstdio>
using namespace std;

stack<string> stk;
string s;
int lson[26], rson[26], val[26], cnt;
void add(char c) {
    int num = c - 'A';
    if (cnt == 0) {
        cnt ++;
        val[cnt] = num;
        lson[cnt] = rson[cnt] = -1;
        return;
    }
    int p = 1;
    while (true) {
        if (num < val[p]) {
            if (lson[p] != -1) p = lson[p];
            else {
                lson[p] = ++cnt;
                val[cnt] = num;
                lson[cnt] = rson[cnt] = -1;
                break;
            }
        }
        else if (num >val[p]) {  // num > val[p]
            if (rson[p] != -1) p = rson[p];
            else {
                rson[p] = ++cnt;
                val[cnt] = num;
                lson[cnt] = rson[cnt] = -1;
                break;
            }
        }
        // num == val[p] 不管 
    }
}
void dfs(int p) {
    putchar('A' + val[p]);
    if (lson[p] != -1) dfs(lson[p]);
    if (rson[p] != -1) dfs(rson[p]);
}
void handle() {
	cnt = 0;
	while (!stk.empty()) {
		string s = stk.top();
		stk.pop();
		int len = s.length();
        for (int i = 0; i < len; i ++) add(s[i]);
	}
    if (!cnt) puts("");
    else {
        dfs(1);
        puts("");
    }
}
int main() {
    while (cin >> s) {
        if (!isupper(s[0])) {
            handle();
        	if (s[0] == '$') break;
		}
        else {
        	stk.push(s);
        }
    }
    return 0;
}