Added code of Wavelet Tree

Data Structures/WaveletTree.cpp

@@ -0,0 +1,130 @@
+#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 deb(x) cout << #x << "=" << x << endl
+#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
+#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>	pl;
+typedef vector<int>		vi;
+typedef vector<ll>		vl;
+typedef vector<pii>		vpii;
+typedef vector<pl>		vpl;
+typedef vector<vi>		vvi;
+typedef vector<vl>		vvl;
+int mpow(int base, int exp); 
+void ipgraph(int m);
+void dfs(int u, int par);
+const int mod = 1000000007;
+const int N = 3e5, M = N;
+//=======================
+const int MAX = 1e6;
+vi g[N];
+int a[N];
+struct wavelet_tree{
+	#define vi vector<int>
+	#define pb push_back
+	int lo, hi;
+	wavelet_tree *l, *r;
+	vi b;
+
+	//nos are in range [x,y]
+	//array indices are [from, to)
+	wavelet_tree(int *from, int *to, int x, int y){
+		lo = x, hi = y;
+		if(lo == hi or from >= to) return;
+		int mid = (lo+hi)/2;
+		auto f = [mid](int x){
+			return x <= mid;
+		};
+		b.reserve(to-from+1);
+		b.pb(0);
+		for(auto it = from; it != to; it++)
+			b.pb(b.back() + f(*it));
+		//see how lambda function is used here	
+		auto pivot = stable_partition(from, to, f);
+		l = new wavelet_tree(from, pivot, lo, mid);
+		r = new wavelet_tree(pivot, to, mid+1, hi);
+	}
+
+	//kth smallest element in [l, r]
+	int kth(int l, int r, int k){
+		if(l > r) return 0;
+		if(lo == hi) return lo;
+		int inLeft = b[r] - b[l-1];
+		int lb = b[l-1]; //amt of nos in first (l-1) nos that go in left 
+		int rb = b[r]; //amt of nos in first (r) nos that go in left
+		if(k <= inLeft) return this->l->kth(lb+1, rb , k);
+		return this->r->kth(l-lb, r-rb, k-inLeft);
+	}
+
+	//count of nos in [l, r] Less than or equal to k
+	int LTE(int l, int r, int k) {
+		if(l > r or k < lo) return 0;
+		if(hi <= k) return r - l + 1;
+		int lb = b[l-1], rb = b[r];
+		return this->l->LTE(lb+1, rb, k) + this->r->LTE(l-lb, r-rb, k);
+	}
+
+	//count of nos in [l, r] equal to k
+	int count(int l, int r, int k) {
+		if(l > r or k < lo or k > hi) return 0;
+		if(lo == hi) return r - l + 1;
+		int lb = b[l-1], rb = b[r], mid = (lo+hi)/2;
+		if(k <= mid) return this->l->count(lb+1, rb, k);
+		return this->r->count(l-lb, r-rb, k);
+	}
+	~wavelet_tree(){
+		delete l;
+		delete r;
+	}
+};
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+	srand(time(NULL));
+	int i,n,k,j,q,l,r;
+	cin >> n;
+	fo(i, n) cin >> a[i+1];
+	wavelet_tree T(a+1, a+n+1, 1, MAX);
+	cin >> q;
+	while(q--){
+		int x;
+		cin >> x;
+		cin >> l >> r >> k;
+		if(x == 0){
+			//kth smallest
+			cout << "Kth smallest: ";
+			cout << T.kth(l, r, k) << endl;
+		}
+		if(x == 1){
+			//less than or equal to K
+			cout << "LTE: ";
+			cout << T.LTE(l, r, k) << endl;
+		}
+		if(x == 2){
+			//count occurence of K in [l, r]
+			cout << "Occurence of K: ";
+			cout << T.count(l, r, k) << endl;
+		}
+	}
+	return 0;
+}