[Tree] [洛谷] P1087 FBI树

建树

输出

#pragma GCC optimize(2)
#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <string>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <ctime>
#include <vector>
#include <fstream>
#include <list>
#include <iomanip>
#include <numeric>
using namespace std;
typedef long long ll;

const int MAXN = 1e6 + 10;

struct node
{
    string trr;
    char type;

}tree[MAXN];

char judge(string x)
{
    bool o = false, z = false;
    for(unsigned int i = 0; i < x.length(); i++)
    {
        if(x[i] == '0')
            o = true;
        if(x[i] == '1')
            z = true;
    }
    if(z && !o)
        return 'I';
    else if(o && !z)
        return 'B';
    else
        return 'F';
}

void build(int now, string x)
{
    tree[now].trr = x;

    tree[now].type = judge(x);
    
    if(x.length() == 1)
        return ;

    string fst = "";

    string lst = "";

    for(unsigned int i = 0; i < x.length() / 2; i++)
        fst = fst + x[i]; 

    for(unsigned int i = x.length() / 2; i < x.length(); i++)
        lst = lst + x[i]; 

    build(now * 2, fst);

    build(now * 2 + 1, lst);

}

void put(int now)
{
    if(tree[now].trr.length() < 1)
        return;
    else
    {
        put(now * 2);
        
        put(now * 2 + 1);

        cout<<tree[now].type;
    }
}



int main()
{
    ios::sync_with_stdio(false);

    cin.tie(0);     cout.tie(0);

    int N;

    cin>>N;

    string x;

    cin>>x;

    build(1, x);

    put(1);

    return 0;
}