[Tree] [洛谷] P1087 FBI树
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#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;
}