POJ3461 Oulipo 字符串

正解:kmp/哈希

解题报告:

传送门!

这题其实就kmp板子,,,用来复习下kmp的太久没打了QAQ

所以kmp做法就不港了放个代码就是了QAQ

#include<algorithm>
#include<iomanip>
#include<cstring>
#include<string>
#include<cstdio>
#include<cmath>
using namespace std;
#define il inline
#define gc getchar()
#define ri register int
#define rb register bool
#define rc register char
#define rp(i,x,y) for(ri i=x;i<=y;++i)
#define my(i,x,y) for(ri i=x;i>=y;--i)

const int N=+;
int nxt[N];
char w[N],t[N];

il int read()
{
    rc ch=gc;ri x=;rb y=;
    while(ch!='-' && (ch>'' || ch<''))ch=gc;
    if(ch=='-')ch=gc,y=;
    while(ch>='' && ch<='')x=(x<<)+(x<<)+(ch^''),ch=gc;
    return y?x:-x;
}
il void getnxt()
{
    ri lth=strlen(w+);
    rp(i,,lth)
    {
        ri nw=nxt[i-];
        while(nw && w[nw+]!=w[i])nw=nxt[nw];
        if(w[nw+]==w[i])++nw;nxt[i]=nw;
    }
}
il int kmp()
{
    ri lthw=strlen(w+),ltht=strlen(t+),i=,j=,as=;
    while(j<=ltht)
    {
        if(w[i]==t[j]){++i;++j;if(i==lthw+)++as,i=nxt[i-]+;}
        else if(i==)++j;else i=nxt[i-]+;
    }
    return as;
}

int main()
{
//    freopen("3461.in","r",stdin);freopen("3461.out","w",stdout);
    ri T=read();
    while(T--)
    {
        memset(nxt,,sizeof(nxt));
        scanf("%s",w+);scanf("%s",t+);
        getnxt();printf("%d\n",kmp());
    }
    return ;
}

然后大概港下哈希滴做法趴

就直接读入,然后对他们分别做哈希,判断一下就好

啊说得有点苍白,,,放下代码趴QAQ

#include<algorithm>
#include<iomanip>
#include<cstring>
#include<string>
#include<cstdio>
#include<cmath>
using namespace std;
#define il inline
#define gc getchar()
#define ri register int
#define rb register bool
#define rc register char
#define ll unsigned long long
#define rp(i,x,y) for(ri i=x;i<=y;++i)
#define my(i,x,y) for(ri i=x;i>=y;--i)

const int N=+,bas=;
int lth_w,lth_t;
ll w_hsh,t_hsh[N],poww;
char w[N],t[N];

il int read()
{
    rc ch=gc;ri x=;rb y=;
    while(ch!='-' && (ch>'' || ch<''))ch=gc;
    if(ch=='-')ch=gc,y=;
    while(ch>='' && ch<='')x=(x<<)+(x<<)+(ch^''),ch=gc;
    return y?x:-x;
}
il ll power(ri gd,ri gs){ll ret=;while(gs){if(gs&)ret=1ll*ret*gd;gd=1ll*gd*gd;gs>>=;}return ret;}

int main()
{
//    freopen("3461.in","r",stdin);freopen("3461.out","w",stdout);
    ri T=read();
    while(T--)
    {
        ri as=;w_hsh=;poww=;
        scanf("%s",w+);scanf("%s",t+);lth_w=strlen(w+);lth_t=strlen(t+);
        rp(i,,lth_w)w_hsh=1ll*w_hsh*bas+w[i];
        rp(i,,lth_t)t_hsh[i]=1ll*t_hsh[i-]*bas+t[i];
        //poww=power(bas,lth_w);
        rp(i,,lth_w)poww=poww*bas;
        rp(i,lth_w,lth_t)if(w_hsh==t_hsh[i]-t_hsh[i-lth_w]*poww)++as;
        printf("%d\n",as);
    }
    return ;
}

有个小细节要注意,写在下面了QwQ

注意一下的是,那个poww不能快速幂,,,会玄学出错,,,就快速幂乘出来的结果都和直接乘不一样,,,我也布吉岛为什么但反正注意一下就是了QAQ