Codeforces Round #116 (Div. 2, ACM-ICPC Rules) D - Name

这题细节真多！！！！

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
#include<cmath>
#include<cassert>
#include<cstring>
#include<iomanip>
using namespace std;

#ifdef _WIN32
#define i64 __int64
#define out64 "%I64d\n"
#define in64 "%I64d"
#else
#define i64 long long
#define out64 "%lld\n"
#define in64 "%lld"
#endif

#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)
#define FF(i,a)         for( int i = 0 ; i < (a) ; i ++)
#define FFD(i,a)        for( int i = (a)-1 ; i >= 0 ; i --)
#define S64(a)          scanf(in64,&a)
#define SS(a)           scanf("%d",&a)
#define LL(a)           ((a)<<1)
#define RR(a)           (((a)<<1)+1)
#define SZ(a)           ((int)a.size())
#define PP(n,m,a)       puts("---");FF(i,n){FF(j,m)cout << a[i][j] << ' ';puts("");}
#define pb              push_back
#define CL(Q)           while(!Q.empty())Q.pop()
#define MM(name,what)   memset(name,what,sizeof(name))
#define read            freopen("in.txt","r",stdin)
#define write           freopen("out.txt","w",stdout)

const int inf = 0x3f3f3f3f;
const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;
const double oo = 10e9;
const double eps = 10e-10;
const double pi = acos(-1.0);

i64 gcd(i64 _a, i64 _b)
{
    if (!_a || !_b)
    {
        return max(_a, _b);
    }
    i64 _t;
    while (_t = _a % _b)
    {
        _a = _b;
        _b = _t;
    }
    return _b;
};

i64 ext_gcd (i64 _a, i64 _b, i64 &_x, i64 &_y)
{
    if (!_b)
    {
        _x = 1;
        _y = 0;
        return _a;
    }
    i64 _d = ext_gcd (_b, _a % _b, _x, _y);
    i64 _t = _x;
    _x = _y;
    _y = _t - _a / _b * _y;
    return _d;
}

i64 invmod (i64 _a, i64 _p)
{
    i64 _ans, _y;
    ext_gcd (_a, _p, _ans, _y);
    _ans < 0 ? _ans += _p : 0;
    return _ans;
}

const int maxn = 5555;

int a[30];
int b[30];
string s;
string t;
string ans;
bool c2;
string a2;

int find(int x)
{
    for(int i=25;i>=x;i--)
    {
        if(a[i]>0)
        {
            return true;
        }
    }
    return false;
}

int f(int x)
{
    for(int i=25;i>x;i--)
    {
        if(a[i]>0)
        {
            return true;
        }
    }
    return false;
}

int re(int x)
{
    for(int i=x+1;i<=25;i++)
    {
        if(a[i]>0)
        {
            return i;
        }
    }
    assert(false);
}
bool can()
{
    int temp;
    int xx;
    for(int i=0;i<t.length();i++)
    {
        temp = t[i] - 'a';
        if(find(temp) && a[temp]>0)
        {
            if(f(temp))
            {
                c2 = true;
                a2 = ans;
                xx =  re(temp);
                a2 += char(xx+'a');
                for(int u=0;u<=25;u++)
                {
                    b[u] = a[u];
                }
                b[xx]--;
            }
            a[temp]--;
            ans+=t[i];
        }
        else if(f(temp))
        {
            xx = re(temp);
            ans += char(xx+'a');
            a[xx]--;
            return true;
        }
        else
        {
            return false;
        }
    }
    return true;
}


int main()
{
    MM(a,0);

    c2 = false;
    ans = "";
    a2 = "";
    cin>>s>>t;

    int temp;
    for(int i=0;i<s.length();i++)
    {
        temp = s[i] - 'a';

        a[temp]++;
    }

    if(!can())
    {
        if(!c2)
        {
            cout<<"-1"<<endl;
        }
        else
        {
            for(int i=0;i<=25;i++)
            {
                while(b[i]>0)
                {
                    a2 += char(i+'a');
                    b[i]--;
                }
            }

            cout<<a2<<endl;
        }
    }
    else
    {
        for(int i=0;i<=25;i++)
        {
            while(a[i]>0)
            {
                char add = i+'a';
                ans += add;
                a[i]--;
            }
        }
        if(ans==t)
        {
            if(!c2)
            {
                cout<<"-1"<<endl;
            }
            else
            {
                for(int i=0;i<=25;i++)
                {
                    while(b[i]>0)
                    {
                        a2 += char(i+'a');
                        b[i]--;
                    }
                }
                cout<<a2<<endl;
            }
        }
        else
        {
            cout<<ans<<endl;
        }
    }
   // system("pause");
    return 0;
}