bzoj3555: [Ctsc2014]企鹅QQ （Hash）

枚举每个分段的点，每次O(n)更新左边和右边的hash值

然后用双指针O(n)计算答案

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
#define ull unsigned long long
using namespace std;
struct HS{
    ull l,r;
}tmp[30010],hs[30010];
ull base,b[202],c[301];
int n,m;
char s[30010][203];

bool cmp(HS a, HS b){
    if (a.l==b.l) return a.r<b.r; return a.l<b.l;
}

bool operator!=(HS a, HS b){
    return ((a.l!=b.l) || (a.r!=b.r));
}

void pre(){
    if (base==2) c['0']=1,c['1']=2;
    else{
        int cnt=0;
        for (int i='A'; i<='Z'; i++) c[i]=++cnt;
        for (int i='a'; i<='z'; i++) c[i]=++cnt;
        for (int i='0'; i<='9'; i++) c[i]=++cnt;
        c['_']=++cnt; c['@']=++cnt;
    }
    ++base; b[0]=1;
    for (int i=1; i<=m; i++) b[i]=b[i-1]*base;
}

int main(){
    scanf("%d%d", &n, &m); cin>>base;
    pre();
    for (int i=1; i<=n; i++){
        scanf("%s", s[i]+1);
        for (int j=2; j<=m; j++)
            hs[i].r=hs[i].r*base+(ull)c[s[i][j]];
    }
    memcpy(tmp,hs,(n+1)*sizeof(HS));
    ull ans=0LL;
    for (int i=2; i<=m+1; i++){
        int head=0;
        sort(hs+1,hs+1+n,cmp);
        for (int j=1; j<=n; j++){
            tmp[j].l=tmp[j].l*base+c[s[j][i-1]];
            tmp[j].r-=b[m-i]*c[s[j][i]];
            if (j==1 || hs[j]!=hs[j-1]) head=j;
            if (j==n || hs[j]!=hs[j+1]) ans+=(ull)(j-head)*(j-head+1)/2;
        }
        memcpy(hs,tmp,(n+1)*sizeof(HS));
    }
    cout<<ans<<endl;
    return 0;
}