Clairewd’s message - HDU 4300（next[]运用）

#include<stdio.h>
#include<string.h>

const int MAXN = 2e5+7;
const int oo = 1e9+7;
const int mod = 10007;

char s[MAXN], a[MAXN], pass[MAXN];
int next[MAXN];

void GetNext(char s[], int N)
{
    int i=0, j=-1;
    next[0] = -1;

    while(i < N)
    {
        if(j==-1 || s[i]==s[j])
            next[++i] = ++j;
        else
            j = next[j];
    }
}

int main()
{
    int T;

    scanf("%d", &T);

    while(T--)
    {
        int i, N, Mid;

        scanf("%s%s", s, a);

        for(i=0; s[i]; i++)
        {
            pass[ s[i]-‘a‘ ] = i+‘a‘;
        }

        N = strlen(a);
        Mid = (N+1)/2;

        for(i=0; i<Mid; i++)
            s[i] = pass[ a[i]-‘a‘ ];
        s[i] = ‘*‘, s[i+1]=0;
        strcat(s, a+i);

        GetNext(s, N+1);

        Mid = N-next[N+1];

        for(i=0; i<Mid; i++)
        {
            s[i] = a[i];
            s[i+Mid] = pass[ a[i]-‘a‘ ];
        }
        s[i+Mid] = 0;

        printf("%s\n", s);
    }
    return 0;
}