Slinding Window

Resources:

GeeksforGeeks

medium

techiedelight.com

leetcodeProblem  Explanation

Some Example:

	class Solution {
	public:
	vector<int> maxSlidingWindow(vector<int>& nums, int k) {
	deque<int> dq;
	vector<int> ans;
	for (int i = 0; i < (int)nums.size(); i++) {
	// remove elements out of window
	if (!dq.empty() && dq.front() == i - k)dq.pop_front();
	/// dq is in descending order (invariant)
	while (!dq.empty() && nums[dq.back()] < nums[i])
	dq.pop_back();
	/// current element push
	dq.push_back(i);
	if (i >= k - 1)
	ans.push_back(nums[dq.front()]);
	}
	return ans;
	}
	};

view raw slidingWindowLeetCode.cpp hosted with ❤ by GitHub

	#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;
	/**___________________________________________________**/
	// Function to find longest substring of given string containing
	// k distinct characters using sliding window
	string longestSubstr(string str, int k, int n)
	{
	int End = 0, Begin = 0;
	unordered_set<char> window;
	int freq[128] = {0};
	for (int l = 0, r = 0; r < n; r++) {
	window.insert(str[r]);
	freq[str[r] - 'a']++;
	while ((int)window.size() > k) {
	if (--freq[str[l] - 'a'] == 0)
	window.erase(str[l]);
	l++;
	}
	if (End - Begin < r - l) {
	End = r;
	Begin = l;
	}
	}
	return str.substr(Begin, End - Begin + 1);
	}
	void findAllanagrams1(string s, string t)
	{
	int n = s.length();
	int m = t.length();
	if (m > n) return;
	/// for count current window character
	unordered_multiset<char> window;
	// maintain count of character in 2nd string
	unordered_multiset<char> sec;
	for (int i = 0; i < (int)t.length(); i++)
	sec.insert(t[i]);
	for (int i = 0; i < n; i++) {
	if (i < m) window.insert(s[i]);
	else {
	if (window == sec) {
	cout << "Angram " << s.substr(i - m, m) << " present at index " <<
	(i - m) << "\n";
	}
	auto it = window.find(s[i - m]);
	if (it != window.end())
	window.erase(it);
	window.insert(s[i]);
	}
	}
	if (window == sec) {
	cout << "Angram " << s.substr(n - m, m) << " present at index " <<
	(n - m) << "\n";
	}
	}
	void findAllanagrams2(string s, string t)
	{
	int n = s.length();
	int m = t.length();
	if (m > n) return;
	for (int i = 0; i <= n - m; i++) {
	if (is_permutation(s.begin() + i, s.begin() + i + m, t.begin())) {
	cout << "Angram " << s.substr(i, m) << " present at index " <<
	i << "\n";
	}
	}
	}
	void longestSubString()
	{
	string str = "abcbdbdbbdcdabd";
	int k = 2;
	int n = str.length();
	cout << longestSubstr(str, k, n) << endl;
	}
	void allSubstringPermutation()
	{
	string s = "XYYZXZYZXXYZ";
	string t = "XYZ";
	findAllanagrams1(s, t);
	cout << "''''''''''''''''''''''\n";
	findAllanagrams2(s, t);
	}
	int main()
	{
	FASTIO
	///*
	#ifndef ONLINE_JUDGE
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	freopen("error.txt", "w", stderr);
	#endif
	//*/
	longestSubString();
	allSubstringPermutation();
	}

view raw techdelight(firstTwo).cpp hosted with ❤ by GitHub

 

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