minor changes wavelet tree

1 files changed, 40 insertions, 46 deletions

diff --git a/datastructures/waveletTree.cpp b/datastructures/waveletTree.cpp
index 36c1b56..4860a40 100644
--- a/datastructures/waveletTree.cpp
+++ b/datastructures/waveletTree.cpp
@@ -1,46 +1,40 @@
-struct WaveletTree {

-	using it = vector<ll>::iterator;

-	WaveletTree *ln, *rn;

-	ll lo, hi;

-	vector<int> b;

-private:

-	WaveletTree(it from, it to, ll x, ll y)

-	: ln(nullptr), rn(nullptr), lo(x), hi(y), b(1) {

-		ll mid = (lo + hi) / 2;

-		auto f = [&](ll x){return x < mid;};

-		for (it c = from; c != to; c++) {

-			b.push_back(b.back() + f(*c));

-		}

-		if (lo + 1 >= hi || from == to) return;

-		it pivot = stable_partition(from, to, f);

-		ln = new WaveletTree(from, pivot, lo, mid);

-		rn = new WaveletTree(pivot, to, mid, hi);

-	}

-public:

-	WaveletTree(vector<ll> in) : WaveletTree(all(in), 

-		*min_element(all(in)), *max_element(all(in)) + 1){}

-

-	// kth element in sort[l, r) all 0-indexed

-	ll kth(int l, int r, int k) {

-		if (l >= r || k >= r - l) return -1;

-		if (lo + 1 >= hi) return lo;

-		int inLeft = b[r] - b[l];

-		if (k < inLeft) {

-			return ln->kth(b[l], b[r], k);

-		} else {

-			return rn->kth(l-b[l], r-b[r], k-inLeft);

-	}}

-

-	// count elements in[l, r) smaller than k

-	int countSmaller(int l, int r, ll k) {

-		if (l >= r || k <= lo) return 0;

-		if (hi <= k) return r - l;

-		return ln->countSmaller(b[l], b[r], k) + 

-		       rn->countSmaller(l-b[l], r-b[r], k);

-	}

-

-	~WaveletTree(){

-		delete ln;

-		delete rn;

-	}

-};

+struct WaveletTree {
+	using it = vector<ll>::iterator;
+	WaveletTree *ln = nullptr, *rn = nullptr;
+	vector<int> b = {0};
+	ll lo, hi;
+
+	WaveletTree(vector<ll> a) : WaveletTree(all(a), // call this
+		*min_element(all(a)), *max_element(all(a)) + 1) {}
+
+	WaveletTree(it from, it to, ll x, ll y) : lo(x), hi(y) {
+		if (lo + 1 >= hi || from == to) return;
+		ll mid = (lo + hi) / 2;
+		auto f = [&](ll x){return x < mid;};
+		for (it c = from; c != to; c++) {
+			b.push_back(b.back() + f(*c));
+		}
+		it pivot = stable_partition(from, to, f);
+		ln = new WaveletTree(from, pivot, lo, mid);
+		rn = new WaveletTree(pivot, to, mid, hi);
+	}
+
+	// kth element in sort[l, r) all 0-indexed
+	ll kth(int l, int r, int k) {
+		if (l >= r || k >= r - l) return -1;
+		if (lo + 1 >= hi) return lo;
+		int inLeft = b[r] - b[l];
+		if (k < inLeft) return ln->kth(b[l], b[r], k);
+		else return rn->kth(l-b[l], r-b[r], k-inLeft);
+	}
+
+	// count elements in[l, r) smaller than k
+	int countSmaller(int l, int r, ll k) {
+		if (l >= r || k <= lo) return 0;
+		if (hi <= k) return r - l;
+		return ln->countSmaller(b[l], b[r], k) +
+		       rn->countSmaller(l-b[l], r-b[r], k);
+	}
+
+	~WaveletTree() {delete ln; delete rn;}
+};