Luogu3435 [POI2006]OKR-Periods of Words (KMP)
\(next\)应用,将原串视作最长前缀复制后的子串
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#define R(a,b,c) for(register int a = (b); a <= (c); ++ a)
#define nR(a,b,c) for(register int a = (b); a >= (c); -- a)
#define Max(a,b) ((a) > (b) ? (a) : (b))
#define Min(a,b) ((a) < (b) ? (a) : (b))
#define Fill(a,b) memset(a, b, sizeof(a))
#define Abs(a) ((a) < 0 ? -(a) : (a))
#define Swap(a,b) a^=b^=a^=b
#define ll long long
#define ON_DEBUG
#ifdef ON_DEBUG
#define D_e_Line printf("\n\n----------\n\n")
#define D_e(x) cout << #x << " = " << x << endl
#define Pause() system("pause")
#define FileOpen() freopen("in.txt","r",stdin);
#else
#define D_e_Line ;
#define D_e(x) ;
#define Pause() ;
#define FileOpen() ;
#endif
struct ios{
template<typename ATP>ios& operator >> (ATP &x){
x = 0; int f = 1; char c;
for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-') f = -1;
while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();
x*= f;
return *this;
}
}io;
using namespace std;
int nxt[1000007];
char str[1000007];
int main(){
int len;
io >> len;
scanf("%s", str);
long long ans = 0;
int i = 0, j = -1;
nxt[0] = -1;
while(i < len){
if(j == -1 || str[i] == str[j]){
nxt[++i] = ++j;
while(nxt[nxt[i]] > 0) nxt[i] = nxt[nxt[i]];
if(nxt[i] > 0){
ans += i -nxt[i];
}
}
else
j = nxt[j];
}
printf("%lld", ans);
return 0;
}