Merge pull request #918 from Es7evam/PersistentSegTree

Add Persistent Segment Tree C++ code

Author: matthewsamuel95

Data Structures/Segment Tree/Persistent_Segment_Tree.cpp

@@ -0,0 +1,67 @@
+#include <bits/stdc++.h>
+ 
+using namespace std;
+ 
+#define pb push_back
+#define mk make_pair
+#define fi first
+#define se second
+ 
+typedef long long ll;
+typedef pair<int, int> ii;
+const int INF = 0x3f3f3f3f;
+const double PI = acos(-1.0);
+ 
+const int N = 1e5 + 5, M = 3e7 + 7;
+int n, a[N];
+int root[N], nodes, L[M], R[M], seg[M];
+ 
+int build (int l, int r) {
+	int at = nodes++;
+ 
+	if (l == r) {
+		seg[at] = a[at];
+	} else {
+		int m = (l + r)/2;
+		L[at] = build (l, m);
+		R[at] = build (m + 1, r);
+		seg[at] = seg[L[at]] + seg[R[at]];
+	}
+ 
+	return at;
+}
+ 
+/* point update, v[p]++ */
+int update (int i, int l, int r, int p) {
+	int at = nodes++;
+ 
+	if (l == r) {
+		seg[at] = seg[i] + 1;
+	} else {
+		int m = (l + r)/2;
+		if (p <= m) {
+			L[at] = update (L[i], l, m, p);
+			R[at] = R[i];
+		} else {
+			L[at] = L[i];
+			R[at] = update (R[i], m + 1, r, p);
+		}
+		seg[at] = seg[L[at]] + seg[R[at]];
+	}
+ 
+	return at;
+}
+ 
+/* range query: v[A] + ... + v[B] */
+int A, B;
+int query (int i, int l, int r) {
+	if (A > B)	return 0;
+	if (r < A or l > B)	return 0;
+ 
+ 	if (l >= A and r <= B) {
+		return seg[i];
+	} else {
+		int m = (l + r)/2;
+		return query (L[i], l, m) + query (R[i], m + 1, r);
+	}
+}