hash+二分求出最長公共字首

然後馬拉車+字首和計數

  1 #include <cstdio>
  2 #include <cstring>
  3 #include <queue>
  4 #include <cmath>
  5 #include <algorithm>
  6 #include <set>
  7 #include <iostream>
  8 #include <map>
  9 #include <stack>
 10
 
 #include <string>
 11 #include <vector>
 12 #define  pi acos(-1.0)
 13 #define  eps 1e-9
 14 #define  fi first
 15 #define  se second
 16 #define  rtl   rt<<1
 17 #define  rtr   rt<<1|1
 18 #define  bug         printf("******\n")
 19 #define  mem(a,b)    memset(a,b,sizeof(a))
 20
 
 #define  name2str(x) #x
 21 #define  fuck(x)     cout<<#x" = "<<x<<endl
 22 #define  f(a)        a*a
 23 #define  sf(n)       scanf("%d", &n)
 24 #define  sff(a,b)    scanf("%d %d", &a, &b)
 25 #define  sfff(a,b,c) scanf("%d %d %d", &a, &b, &c)
 26 #define
 
  sffff(a,b,c,d) scanf("%d %d %d %d", &a, &b, &c, &d)
 27 #define  pf          printf
 28 #define  FRE(i,a,b)  for(i = a; i <= b; i++)
 29 #define  FREE(i,a,b) for(i = a; i >= b; i--)
 30 #define  FRL(i,a,b)  for(i = a; i < b; i++)+
 31 #define  FRLL(i,a,b) for(i = a; i > b; i--)
 32 #define  FIN         freopen("data.txt","r",stdin)
 33 #define  gcd(a,b)    __gcd(a,b)
 34 #define  lowbit(x)   x&-x
 35 using namespace std;
 36 typedef long long  LL;
 37 typedef unsigned long long ULL;
 38 const int mod = 1e9 + 7;
 39 const int maxn = 2e5 + 10;
 40 const int INF = 0x3f3f3f3f;
 41 const LL INFLL = 0x3f3f3f3f3f3f3f3fLL;
 42 int lens, lent;
 43 char s[maxn << 1], t[maxn], ss[maxn << 1];
 44 int d[maxn], r[maxn << 1];
 45 
 46 int Init() {
 47     int len = strlen ( s + 1 );
 48     ss[0] = '$';
 49     ss[1] = '#';
 50     int j = 2;
 51     for ( int i = 1; i <= len; i++ ) ss[j++] = s[i], ss[j++] = '#';
 52     ss[j] = '\0';
 53     return j;
 54 }
 55 void Manacher() {
 56     int len = Init();
 57     int p, mx = 0;
 58     for ( int i = 1; i < len; i++ ) {
 59         if ( i < mx ) r[i] = min ( r[2 * p - i], mx - i );
 60         else r[i] = 1;
 61         while ( ss[i - r[i]] == ss[i + r[i]] ) r[i]++;
 62         if ( mx < i + r[i] ) p = i, mx = i + r[i];
 63     }
 64     for ( int i = 2; i < len; i++ ) {
 65         if ( ss[i] == '#' && r[i] == 1 ) continue;
 66         int x = i / 2 - r[i] / 2 + 1, y = i / 2 + r[i] / 2 - ! ( i & 1 );
 67         d[x]++;
 68         d[ ( x + y ) / 2 + 1]--;
 69     }
 70 }
 71 ULL p[maxn], h1[maxn], h2[maxn],seed=131;
 72 
 73 ULL getkey ( ULL *a, int l, int r ) {
 74     return ( a[r] - a[l - 1] * p[r - l + 1] );
 75 }
 76 bool check ( int len, int P, int lent ) {
 77     if ( getkey ( h1, P - len + 1, P ) == getkey ( h2, lent - len + 1, lent ) ) return true;
 78     return false;
 79 }
 80 int main() {
 81     p[0] = 1;
 82     for ( int i = 1; i < maxn; i++ ) p[i] = p[i - 1] * seed  ;
 83     while ( ~scanf ( "%s%s", s + 1, t + 1 ) ) {
 84         lens = strlen ( s + 1 );
 85         lent = strlen ( t + 1 );
 86         for ( int i = 1; i <= lens; i++ ) d[i] = 0;
 87         Manacher();
 88         for ( int i = 1; i <= lens; i++ ) d[i] += d[i - 1];
 89         reverse ( t+1, t + lent+1 );
 90         for ( int i = 1; i <= lens; ++i ) h1[i] = ( h1[i-1] * seed + s[i] ) ;
 91         for ( int i = 1; i <= lent; ++i ) h2[i] = ( h2[i-1] * seed + t[i] ) ;
 92         LL res = 0;
 93         for ( int i = 1; i < lens; ++i ) {
 94             if ( s[i] != t[lent] ) continue;
 95             int l = 1, r = min ( lent, i+1 ), mid, ans = 0;
 96             while ( r >= l ) {
 97                 mid = ( l + r ) >> 1;
 98                 if ( check ( mid, i, lent ) ) ans = mid, l = mid + 1;
 99                 else r = mid - 1;
100             }
101             res += ( LL ) ans * d[i + 1];
102         }
103         printf ( "%lld\n", res );
104     }
105 }