poj_3450 Corporate Identity（KMP+枚举）

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

char a[4002][201];
int next[202];

void getNext(char t[], int x, int y)
{
int i=x, j=x-1; next[i]=j;

while (i<y+1)
if (j==x-1 || t[i]==t[j])
{
i++;j++;
if (t[i]!=t[j]) next[i]=j; else next[i]=next[j];
}
else j=next[j];
}

int kmpMain(char t[], int x, int y, char s[])
{
int i=0, j=x, sLen=strlen(s);

while (i<sLen && j<y+1)
if (j==x-1 || s[i]==t[j]){i++;j++;}
else j=next[j];

if (j==y+1) return 1;
else return -1;
}

int comp(char s[], int x, int y, int len)
{
int i, ans=x;
for (i=0;i<len;i++)
{
if (s[x+i]<s[y+i]) {ans=x;break;}
if (s[x+i]>s[y+i]) {ans=y;break;}
}
return ans;
}

int main()
{
int m,i,j,k;
while (1)
{
scanf("%d",&m);
if (m==0) break;
scanf("%s",a[1]); int small=strlen(a[1]), ls=1;
for (j=2;j<=m;j++) {scanf("%s",a[j]); int sLen=strlen(a[j]); if (sLen<small){small=sLen; ls=j;}}
strcpy(a[0],a[ls]);
int flag=0,ans;
for (j=small;j>0;j--)
{
for (k=0;k<=small-j;k++)
{
getNext(a[0],k,k+j-1);
int flag1=0,p;
for (p=1;p<=m;p++) if (kmpMain(a[0],k,k+j-1,a[p])<0) {flag1=1;break;}
if (flag1==0)
if (flag==0) {flag=1;ans=k;} else ans=comp(a[0],ans,k,j);
}
if (flag==1)
{
for (k=ans;k<ans+j;k++) printf("%c",a[0][k]);
printf("\n");
break;
}
}
if (flag==0) printf("IDENTITY LOST\n");
}
return 0;
}