SCU-4438 Censor(KMP算法)

Censor

frog is now a editor to censor so-called sensitive words (敏感词).

She has a long text p p. Her job is relatively simple -- just to find the first occurence of sensitive word w w and remove it.

frog repeats over and over again. Help her do the tedious work.

Input

The input consists of multiple tests. For each test:

The first line contains 1 1 string w w. The second line contains 1 1 string p p.

(1≤length of w,p≤5⋅10 6  1≤length of w,p≤5⋅106, w,p w,p consists of only lowercase letter)

Output

For each test, write 1 1 string which denotes the censored text.

Sample Input

    abc
    aaabcbc
    b
    bbb
    abc
    ab

Sample Output

    a
    
    ab

题意:给出2个字符串,第一个字符串P是第二个字符串的敏感词,如果第二个字符串出现了P就要删除,后面的字符补到前面去,问最后剩下的字符串是什么
题解:KMP算法,用数组模拟栈储存要输出的字符串,index表示单签储存了几个字符,如果遇到要删除的字符串,则index-P的长度,然后继续更新,关于KMP算法的
话,如果不懂就先网上搜索下资料吧,这个算法我还不能很好地总结.

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
const int maxn = 5e6 + 5;
int Next[maxn],tmp[maxn];
void makeNext(const char P[]){
    int q,k;
    int m=strlen(P);
    memset(Next,0,sizeof(Next));
    Next[0]=0;
    for(q=1,k=0;q0&&P[q]!=P[k])
            k=Next[k-1];
        if(P[q]==P[k]) k++;
        Next[q]=k;
    }
}
char st[maxn];
int KMP(const char T[],const char P[]){
    int n=strlen(T),m=strlen(P),q=0,index=0;
    makeNext(P);
    for(int i=0;i0&&P[q]!=T[i])
            q=Next[q-1];
        if(P[q]==T[i]) q++;
        tmp[index]=q;//记录第index个字符的部分匹配值
        if(q==m) {
            index-=m;//匹配成功时,删去最后m个字符,继续匹配
            q=tmp[index];//将index的部分匹配值给q
        }
    }
    return index;
}
char st1[maxn],st2[maxn];
int main(){
   // freopen("in.txt","r",stdin);
    while(~scanf("%s%s",st1,st2)){
        st[KMP(st2,st1)]='\0';
        printf("%s\n",st);
    }
    return 0;
}