poj 1577 Falling Leaves

#include <iostream>#include <cstdlib>#include <cstdio>#include <cstring>using namespace std;#define maxn 105struct Node{    Node *left, *right;    char letter;}tree[maxn];char st[maxn];int node_cnt;void insert(Node * &proot, char ch){    if (proot == NULL)    {        proot = &tree[node_cnt++];        proot->left = NULL;        proot->right = NULL;        proot->letter = ch;        return;    }    if (ch > proot->letter)        insert(proot->right, ch);    else        insert(proot->left, ch);}void output(Node *proot){    putchar(proot->letter);    if (proot->left)        output(proot->left);    if (proot->right)        output(proot->right);}void input(){    char *p = st;    while (1)    {        scanf("%s", p);        if (*p == '*') return;        if (*p == '$') return;        p = st + strlen(st);        }}int main(){    while (1)    {        input();        Node *proot = NULL;        node_cnt = 0;        for (int i = strlen(st) - 2; i >= 0; i--) insert(proot, st[i]);        output(proot);        putchar('n');        if (st[strlen(st) - 1] == '$') break;    }    return 0;}