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;

}

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Luogu3435 [POI2006]OKR-Periods of Words （KMP）

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