Merge pull request rachitiitr#6 from rachitkewl/master

Added Sliding Window

Author: rachitiitr

Miscellanious/sliding_window.cpp

@@ -0,0 +1,82 @@
+//sliding window maximum
+//https://people.cs.uct.ac.za/~ksmith/articles/sliding_window_minimum.html
+//http://codeforces.com/problemset/problem/372/C
+#include <bits/stdc++.h>
+using namespace std;
+#define gc getchar_unlocked
+#define fo(i,n) for(i=0;i<n;i++)
+#define Fo(i,k,n) for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
+#define ll long long
+#define si(x)	scanf("%d",&x)
+#define sl(x)	scanf("%lld",&x)
+#define ss(s)	scanf("%s",s)
+#define pi(x)	printf("%d\n",x)
+#define pl(x)	printf("%lld\n",x)
+#define ps(s)	printf("%s\n",s)
+#define pb push_back
+#define mp make_pair
+#define F first
+#define S second
+#define all(x) x.begin(), x.end()
+#define clr(x) memset(x, 0, sizeof(x))
+#define sortall(x) sort(all(x))
+#define tr(it, a) for(auto it = a.begin(); it != a.end(); it++)
+#define PI 3.1415926535897932384626
+typedef pair<int, int>	pii;
+typedef pair<ll, ll>	pll;
+typedef vector<int>		vi;
+typedef vector<ll>		vll;
+typedef vector<pii>		vpii;
+typedef vector<pll>		vpll;
+typedef vector<vi>		vvi;
+typedef vector<vll>		vvl;
+const int mod = 1000000007;
+const int N = 3e5;
+vi g[N];
+ll a[N], b[N], t[N];
+ll dp[3][N];
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+	int i,n,k,j,m,d;
+	cin>>n>>m>>d;
+	fo(i, m) cin>>a[i]>>b[i]>>t[i];
+	int cur = 1, pre = 0;
+	Fo(i, 1, n+1)
+		dp[cur][i] = b[m-1]-abs(a[m-1]-i);
+	swap(cur, pre);
+	Fo(i, m-2, -1){
+		deque<pll> window;
+		ll dt = t[i+1]-t[i];
+		dt *= d;
+		k = min(n-1LL, dt);
+		//moving from right to left
+		//initially install [n-k+1, n] 
+		//j-k to j+k
+		Fo(j, n, n-k){
+			while(!window.empty() and window.back().F <= dp[pre][j])
+				window.pop_back();	
+			window.pb({dp[pre][j], j});
+		}
+		Fo(j, n, 0){
+			
+			int x = j-k;
+			//add j-k to window
+			if (x>0) {
+				while(!window.empty() and window.back().F <= dp[pre][x])
+					window.pop_back();
+				window.pb({dp[pre][x], x});
+			}
+			//remove elements at pos > j+k
+			while(!window.empty() and window.front().S > j+k) window.pop_front();
+			dp[cur][j] = b[i]-abs(a[i]-j) + window.front().F;
+		}
+		swap(cur, pre);
+	}
+	ll ans = -1e17;
+	Fo(i, 1, n+1) ans = max(ans, dp[pre][i]);
+	cout<<ans<<endl;
+	return 0;
+} 
+