【模板】KMP

题意简述

给出两个字符串s1和s2，其中s2为s1的子串，求出s2在s1中所有出现的位置。

代码

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
int nxt[1000010];
char st1[1000010], st2[1000010];
void cnxt(char* st, int l)
{
	int x = -1;
	nxt[0] = -1;
	for (register int i = 1; i < l; ++i)
	{
		while (x > -1 && st[i] != st[x + 1]) x = nxt[x];
		if (st[i] == st[x + 1]) ++x;
		nxt[i] = x;
	}
}
void kmp(char* st1, int l1, char* st2, int l2)
{
	int x = -1;
	cnxt(st2, l2);
	for (register int i = 0; i < l1; ++i)
	{
		while (x > -1 && st1[i]!=st2[x + 1]) x = nxt[x];
		if (st1[i] == st2[x + 1]) ++x;
		if (x == l2 - 1) printf("%d\n", i - l2 + 2);
	}
}
int main()
{
	ios::sync_with_stdio(false);
	cin >> st1 >> st2;
	kmp(st1, strlen(st1), st2, strlen(st2));
}