[KMP: The longest public substring of multiple strings] poj 3450

Strange, this question is modified by poj3080 and AC, but it cannot be used in poj3080. It is strange to say that... Is the RP of Brother's low to this ?!

#include <map>#include <set>#include <list>#include <queue>#include <deque>#include <stack>#include <string>#include <time.h>#include <cstdio>#include <math.h>#include <iomanip>#include <cstdlib>#include <limits.h>#include <string.h>#include <iostream>#include <fstream>#include <algorithm>using namespace std;#define LL long long#define MIN INT_MIN#define MAX INT_MAX#define PI acos(-1.0)#define FRE freopen("input.txt","r",stdin)#define FF freopen("output.txt","w",stdout)#define N 205char str[4005][N];int p[N];int m;int l[N];bool chk(char *ss) {    int i,j;    int len = strlen(ss+1);    p[1] = 0;    j = 0;    for (i = 2; i <= len; i++) {        while (j > 0 && ss[i] != ss[j+1]) {            j = p[j];        }        if (ss[i] == ss[j+1]) j++;        p[i] = j;    }    for (int kk = 2; kk <= m; kk++) {        j = 0;        for (i = 1; i <= l[kk]; i++) {            while (j > 0 && ss[j+1] != str[kk][i]) {                j = p[j];            }            if (ss[j+1] == str[kk][i]) j++;            if (j == len) break;        }        if (i > l[kk])return false;    }    return true;}int main () {    while (scanf("%d",&m) && m) {        int i,j;//        for (i = 1; i <= m; i++) {            scanf("%s",str[i]+1);            l[i] = strlen(str[i]+1);            //printf("!%s\n",str[i]+1);        }        char ss[N],ans[N];        int maxlen = 0;        memset(ans,'\0',sizeof(ans));        for (int len = 1; len <= l[1]; len++) {            for (i = 1; i + len <= l[1] + 1; i++) {                int cnt = 1;                for (j = i; j  <= len + i - 1; j++) {                    ss[cnt++] = str[1][j];                }                ss[cnt] = '\0';//printf("!%s\n",ss+1);                if (chk(ss)) {                        if (len == maxlen) {                            if (strcmp(ans+1,ss+1) > 0) {                                strcpy(ans+1,ss+1);                            }                        } else if (len > maxlen) {                            maxlen = len;                            strcpy(ans+1,ss+1);                        }                }            }        }        if (strlen(ans+1) == 0) puts("IDENTITY LOST");        else printf("%s\n",ans+1);    }    return 0;}