SCU 4438:Censor

Censor

frogisnowaeditortocensorso-calledsensitivewords(敏感词).

Shehasalongtextp

.Herjobisrelativelysimple--justtofindthefirstoccurenceofsensitivewordw

andremoveit.

frogrepeatsoverandoveragain.Helpherdothetediouswork.

Input

Theinputconsistsofmultipletests.Foreachtest:

Thefirstlinecontains1

stringw.Thesecondlinecontains1stringp

.

(1≤lengthofw,p≤5⋅106

,w,p

consistsofonlylowercaseletter)

Output

Foreachtest,write1

stringwhichdenotesthecensoredtext.

SampleInput

abc
aaabcbc
b
bbb
abc
ab

SampleOutput

a

ab

题意:给你一个主串,递归删除模式串。
比如:T:abcS:aaabcbc
aaabcbc->aabc->a

非常巧妙的KMP,我们用一个栈记录当前的字符以及其在模式串匹配的位置,当位置等于模式串长度之后,将模式串长度的串出栈,从栈顶元素开始继续匹配主串.时间复杂度O(n).

#include<stdio.h>
#include<iostream>
#include<string.h>
#include<stack>
#include<algorithm>
usingnamespacestd;
constintN=5000005;
structNode{
charc;
intk;
};
charw
,t
,ans
;
intNext
;
voidget_next(char*p){
intlen=strlen(p);

inti=0,k=-1;
Next[0]=-1;
while(i<len){
if(k==-1||p[i]==p[k]){
i++,k++;
Next[i]=k;
}
elsek=Next[k];
}
}

voidKmp(char*s,char*p){
intlen1=strlen(s),len2=strlen(p);
inti=0,j=0,len;
stack<Node>stk;
while(!stk.empty())stk.pop();
while(i<len1){
if(j==-1||s[i]==p[j]){
i++,j++;
stk.push(Node{s[i-1],j});
}else{
j=Next[j];
}
if(j==len2){
len=len2;
while(!stk.empty()&&len--)stk.pop();
if(stk.empty())j=0;
elsej=stk.top().k;
}
}
intk=0;
while(!stk.empty()){
ans[k++]=stk.top().c;
stk.pop();
}
for(inti=k-1;i>=0;i--)printf("%c",ans[i]);
printf("\n");
}
intmain(){
while(scanf("%s%s",w,t)!=EOF){
get_next(w);
Kmp(t,w);
}
return0;
}