Z Algorithm

Resources:

tushar roy

Z-function and its calculation 

Shakil Ahmed (bangla blog) 

Animation

Linear-time pattern matching. Z-values and Z-algorithm

Finish of Linear-time pattern matching

Z Algorithm ( HackerEarth)

GeeksforGeeks

pdf

Ivan Yurchenko blog

 

Implematation:

	#include <bits/stdc++.h>
	using namespace std;
	#define INF 1<<30
	#define endl '\n'
	#define maxn 100005
	#define tc printf("Case %d: ", cs)
	#define tcn printf("Case %d:\n", cs);
	#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	typedef long long ll;
	const double PI = acos(-1.0);
	#define dbg1(x) cerr << #x << " = " << x << endl;
	#define dbg2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl;
	#define dbg3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	#define dbg4(w,x, y, z) cerr << #w << " = " << w << ", " <<#x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	template < typename F, typename S >
	ostream& operator << ( ostream& os, const pair< F, S > & p ) {
	return os << "(" << p.first << ", " << p.second << ")";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const vector< T > &v ) {
	os << "{";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << *it;
	}
	return os << "}";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const set< T > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin()) os << ", ";
	os << *it;
	}
	return os << "]";
	}
	template < typename F, typename S >
	ostream &operator << ( ostream & os, const map< F, S > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << it -> first << " = " << it -> second ;
	}
	return os << "]";
	}
	#define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)
	clock_t tStart = clock();
	#define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)
	void faltu () { cerr << endl; }
	template <typename T>
	void faltu( T a[], int n ) {
	for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
	cerr << endl;
	}
	template <typename T, typename ... hello>
	void faltu( T arg, const hello &... rest) { cerr << arg << ' '; faltu(rest...); }
	// Program showing a policy-based data structure.
	#include <ext/pb_ds/assoc_container.hpp> // Common file
	#include <ext/pb_ds/tree_policy.hpp>
	#include <functional> // for less
	#include <iostream>
	using namespace __gnu_pbds;
	using namespace std;
	// GNU link : https://goo.gl/WVDL6g
	typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
	tree_order_statistics_node_update>
	new_data_set;
	/**___________________________________________________**/
	vector<int> z_function(string s) // from E-maxx
	{
	int n = (int) s.length();
	vector<int> z(n);
	for (int i = 1, l = 0, r = 0; i < n; i++) {
	if (i <= r)
	z[i] = min(r - i + 1, z[i - l]);
	while (i + z[i] < n && s[z[i]] == s[i + z[i]])
	++z[i];
	if (i + z[i] - 1 > r) {
	l = i;
	r = i + z[i] - 1;
	}
	}
	return z;
	}
	vector<int> z_algo(string s) // from tushar roy video
	{
	int n = s.length();
	vector <int> z(n);
	int l = 0, r = 0;
	for (int k = 1; k < n; k++) {
	if (k > r) {
	l = r = k;
	while (r < n && s[r] == s[r - l]) r++;
	z[k] = r - l;
	r--;
	}
	else {
	// inside box
	int i = k - l;
	if (z[i] < r - k + 1) z[k] = z[i];
	else {
	l = k;
	while (r < n && s[r] == s[r - l]) r++;
	z[k] = r - l;
	r--;
	}
	}
	}
	return z;
	}
	int main()
	{
	FASTIO
	///*
	#ifndef ONLINE_JUDGE
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	freopen("error.txt", "w", stderr);
	#endif
	//*/
	string text;// pattern;
	cin >> text ;//>> pattern;
	//text += "$" + pattern;
	auto ans = z_function(text);
	for (auto x : ans) cerr << x << " ";
	/// No output, just z array---
	}

view raw z_Algorithm.cpp hosted with ❤ by GitHub

 

Problems: 

E-maxx blog 

hackerEarth 

string algo 

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