codeforces 559b//Equivalent Strings// Codeforces Round #313(Div. 1)

题意：定义了字符串的相等，问两串是否相等。

卡了时间，空间，不能新建字符串，否则会卡。

#pragma comment(linker,"/STACK:1024000000,1024000000") 
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<vector>
#include<cmath>
#include<queue>
#include<stack>
#include<map>
#include<set>
#include<algorithm>
#include <stack>
using namespace std;
const int SZ=1e7+10,INF=0x7FFFFFFF;
typedef long long lon;
string x,y;

bool cmp(int bg1,int end1,int bg2,int end2)
{
    for(int i=bg1,j=bg2;i<end1;++i,++j)
    {
        if(x[i]!=y[j])return 1;
    }
    return 0;
}

bool equ(int bg1,int end1,int bg2,int end2,int d)
{
    int len=end1-bg1;
    //cout<<d<<"cmp: "<<bg1<<" "<<end1<<" "<<bg2<<" "<<end2<<" "<<cmp(bg1,end1,bg2,end2)<<endl;
    if(cmp(bg1,end1,bg2,end2)==0)return 1;
    else if((len)&1)return 0;
    else
    {
        int half=len/2;
        return (equ(bg1,bg1+half,bg2,bg2+half,d+1)&&equ(bg1+half,end1,bg2+half,end2,d+1)||equ(bg1,bg1+half,bg2+half,end2,d+1)&&equ(bg1+half,end1,bg2,bg2+half,d+1));
    }
}

int main()
{
    std::ios::sync_with_stdio(0);
    cin>>x>>y;
    if(equ(0,x.size(),0,y.size(),0))cout<<"YES"<<endl;
    else cout<<"NO"<<endl;
    return 0;
}