Implementing KMP string matching.cpp

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;

#include<bits/stdc++.h>
#include<cmath>
#include<cstdlib> //for qsort
#include<cstdio>

#define rep(x,a,b) for(x=a;x<b;x++)
#define reptill(x,a,b) for(x=a;x<=b;x++)

#define scani(x) scanf("%d",&x)
#define scan2i(x,y) scanf("%d %d",&x,&y)
#define scan3i(x,y,z) scanf("%d %d %d",&x,&y,&z)

#define scanfl(x) scanf("%f",&x)
#define scanc(x) scanf("%c",&x)
#define scand(x) scanf("%lf",&x)

#define scanll(x) scanf("%lli",&x)
#define scan2ll(x,y) scanf("%lli %lli",&x,&y)
#define scan3ll(x,y) scanf("%lli %lli %lli",&x,&y,&z);

#define scanl(x) scanf("%ld",&x)
#define scans(x) scanf("%s",x)
#define printi(x) printf("%d\n",x)
#define printl(x) printf("%ld\n",x)
#define printll(x) printf("%lli\n",x)
#define printd(x) printf("%lf\n",x)
#define printfl(x) printf("%f\n",x)
#define printc(x) printf("%c\n",x)
#define prints(x) printf("%s\n",x);
#define sloop(x) loop(i,0,strlen(x)-1)
#define newl cout<<"\n"
#define FILL(A,value) memset(A,value,sizeof(A))


#define whole(x) x.begin(),x.end()
#define pb push_back


using namespace std;


#define F first
#define S second

typedef pair<int,int> ii;
typedef vector<ii> vii;



inline bool inc_range(int x,int y,int z) { return ((x>=y)&&(x<=z)); }
inline bool ex_range(int x,int y,int z) { return ((x>y)&&(x<z)); }
inline bool is_either(int x,int y,int z) { return ((x==y)||(x==z)); }

//maths
#define PI acos(-1)

#define INTmax numeric_limits<int>::max()
#define LLmax numeric_limits<ll>::max()
#define ULLmax numeric_limits<ull>::max()

#define INTmin numeric_limits<int>::min()


typedef priority_queue<ii,vector<ii>, greater<ii> > P_Queue;             ///priority queue contianing ii (having vector<ii> as underlying container) with greater as functor
																		///		heapify on the basis of comparisons of  ii.first  values

template<typename type>
void get_arr(type a[],type n) {for(type i=0;i<n;i++) cin>>a[i];}

template<typename type>
void show_arr(type a[],type n=1) {for(type i=0;i<n;i++) cout<<a[i]<<" ";}

template<typename type>
inline type max3(type a,type b,type c){	 return max(max(a,b),c);}

template<typename type>
inline type min3(type a,type b,type c){	 return min(a,min(b,c));}

template<typename type>
inline type min4(type a,type b,type c,type d){	 return min(a,min3(b,c,d));}


template<typename type>
type fastpow(type a, type b, type c) { type ans=1;  while(b != 0){ if(b%2 == 1) ans=(ans*a)%c;  a=(a*a)%c; b /= 2; } return ans; }

template<typename type>
type phi(type n){ type result = n;  for (type p=2; p*p<=n; ++p) { if (n % p == 0){ while (n % p == 0)   n /= p; result -= result / p; } }
if (n > 1) result -= result / n; return result;
}

template<class type>
type ncr(type n,type r)
{  	assert(n>=r);
	type ans=1,i;
	if(n==r) return 1; if(r==1) return n; if(r>(n-r)) r=n-r;
	reptill(i,0,r-1) ans=ans*(n-i)/(i+1);
	return ans;
}

inline void FAST_IO(){ios_base::sync_with_stdio(false);}



#define SIZE int(2e3)+1
#define MOD
#define debug


//#define Online_judge
void failure_func(string pat,vector<int> & lps)
{
	int j=0,i=1;
	lps[0]=0;

	//for(int i=1;i<pat.size() and j>=0;i++)
	while(i<pat.size())
	{

		if(pat[j]==pat[i])
		{
			lps [i]=j+1;
			j++; i++;
		}
		else
		{
				if(j) j=lps[j-1];
				else{ lps[i]=0;

				i++;
				}
		}
	}
}


int kmpmatch(string const& pat,string  const& txt,vector<int> &pos,vector<int> &lps)
{

	int i = 0,j=0;

	while(i<txt.size())
    {
        if(pat[j]==txt[i])
        {
            j++;
            i++;
        }


        if(j==pat.size())
        {
            pos.pb(i-j);
            j = lps[j-1];
        }
        else if(i<txt.size() && pat[j]!=txt[i])
        {
            if (j!=0)
                j=lps[j-1];
            else
                i++;
        }
    }

}

int main()
{
	FAST_IO();

	ifstream cin("ip");
	//ofstream cout("op");

    string p,t;

    cin>>p>>t;

	vector<int> lps(p.size()),v;

    failure_func(p,lps);


	kmpmatch(p,t,v,lps);

	for(auto x:v)
    {
		cout<<x<<" ";
    }

}