KMP——Game

Problem 2275 Game

Accept: 41    Submit: 109
Time Limit: 1000 mSec    Memory Limit : 262144
KB

Problem Description

Alice and Bob is playing a game.

Each of them has a number. Alice’s number is A, and Bob’s number is B.

Each turn, one player can do one of the following actions on his own
number:

1. Flip: Flip the number. Suppose X = 123456 and after flip, X = 654321

2. Divide. X = X/10. Attention all the numbers are integer. For example
X=123456 , after this action X become 12345（but not 12345.6）. 0/0=0.

Alice and Bob moves in turn, Alice moves first. Alice can only modify A, Bob
can only modify B. If A=B after any player’s action, then Alice win. Otherwise
the game keep going on!

Alice wants to win the game, but Bob will try his best to stop Alice.

Suppose Alice and Bob are clever enough, now Alice wants to know whether she
can win the game in limited step or the game will never end.

Input

First line contains an integer T (1 ≤ T ≤ 10), represents there are T test
cases.

For each test case: Two number A and B. 0<=A,B<=10^100000.

Output

For each test case, if Alice can win the game, output “Alice”. Otherwise
output “Bob”.

Sample Input

4
11111 1
1 11111
12345 54321
123 123

Sample Output

Alice
Bob
Alice
Alice

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
char s[1000005],t[1000005],tmp[1000005];
int nextl[1000005];
int ls,lt;
void getnext()
{
    nextl[0]=-1;
    for(int i=1;i<lt;i++)
    {
        int j=nextl[i-1];
        while(t[j+1]!=t[i]&&j>-1)
            j=nextl[j];
        nextl[i]=(t[j+1]==t[i])?j+1:-1;
    }
}
int kmp(char *a,char *b)
{
    getnext();
    int sum=0,i=0,j=0;
    while(i<ls&&j<lt)
    {
        if(j==-1||a[i]==b[j])
            i++,j++;
        else
            j=nextl[j];
    }
    if(j==lt)
        return 1;
    return 0;
}
int main()
{
    int n;
    cin>>n;
    while(n--)
    {
        cin>>s>>t;
        ls=strlen(s),lt=strlen(t);
        if(ls<lt)
        {
            printf("Bob\n");
            continue;
        }
        if(kmp(s,t)||!strcmp(t,"0"))
        {
            printf("Alice\n");
            continue;
        }
        reverse(t,t+lt);
        if(kmp(s,t))
        {
            printf("Alice\n");
            continue;
        }
        printf("Bob\n");
    }
    return 0;
}