Luogu P1305 New Binary Tree

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Topic description

Input a string of binary trees and print them out with traversal preorder.

Input and output format

Input format:

The first line is the number of nodes n of the binary tree. (  $n\le 26$ )

In the next n lines, each letter is a node, and the last two letters are its left and right sons respectively.

Empty nodes are represented by *

Output format:

preorder binary tree

Input and output example

Input example #1: 

6
abc
bdi
cj*
d**
i**
j**

Sample output #1: 

abdicj

Ideas:

Simple pre-order traversal of binary tree, the key point is that I am a konjac who does not know all kinds of knowledge about character classes, so I have to roughly convert char to int...

Code:

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

#define maxn 250
#define loop( i, a, b )	for( int i = a; i <= b; i++ )

using namespace std;

int n, kong = '*' - '0';
int f[maxn], v[maxn], l[maxn], r[maxn];

void haha_tree() {
	char p, lc, rc;
	scanf( "%d", &n );
	loop( i, 1, n ) {
		cin>>p>>lc>>rc;
		int llc, rrc, pp;
		pp = p - '0'; //Rough transformation.
		llc = lc - '0';
		rrc = rc - '0';
		if( llc != kong ) {
			f[llc] = pp;
			l[pp] = llc;
		}
		if( rrc != kong ) {
			f[rrc] = pp;
			r[pp] = rrc;
		}
	}
}

inline int find_root() { //Why do you force me to write a board?
	int aa = 'a' - '0'; // Still rough.
	int bb = 'z' - '0';
	loop( i, aa, bb )
		if( f[i] == 0 )
			return i;
}

inline void xianxu( int i ) {
	if( i ) {
		chariot years;
		years = i + '0';
		cost<<years;
		xianxu( l[i] );
		xianxu( r[i] );
	}
}

int main() {
	haha_tree();
	int gen = find_root();
	xianxu( gen );
	return 0;
}