Merge pull request #310 from sumant7/sumant7

Sumant7

C++/segment.cpp

@@ -0,0 +1,104 @@
+// C++ code for segment tree with sum
+// range and update query
+
+#include <bits/stdc++.h>
+using namespace std;
+vector<int> A, ST;
+
+void build(int node, int L, int R)
+{
+
+	// Leaf node where L == R
+	if (L == R) {
+		ST[node] = A[L];
+	}
+	else {
+
+		// Find the middle element to
+		// split the array into two halves
+		int mid = (L + R) / 2;
+
+		// Recursively travel the
+		// left half
+		build(2 * node, L, mid);
+
+		// Recursively travel the
+		// right half
+		build(2 * node + 1, mid + 1, R);
+
+		// Storing the sum of both the
+		// children into the parent
+		ST[node] = ST[2 * node] + ST[2 * node + 1];
+	}
+}
+
+void update(int node, int L, int R, int idx, int val)
+{
+
+	// Find the lead node and
+	// update its value
+	if (L == R) {
+		A[idx] += val;
+		ST[node] += val;
+	}
+	else {
+
+		// Find the mid
+		int mid = (L + R) / 2;
+
+		// If node value idx is at the
+		// left part then update
+		// the left part
+		if (L <= idx and idx <= mid)
+			update(2 * node, L, mid, idx, val);
+		else
+			update(2 * node + 1, mid + 1, R, idx, val);
+
+		// Store the information in parents
+		ST[node] = ST[2 * node] + ST[2 * node + 1];
+	}
+}
+
+int query(int node, int tl, int tr, int l, int r)
+{
+
+	// If it lies out of range then
+	// return 0
+	if (r < tl or tr < l)
+		return 0;
+
+	// If the node contains the range then
+	// return the node value
+	if (l <= tl and tr <= r)
+		return ST[node];
+	int tm = (tl + tr) / 2;
+
+	// Recursively traverse left and right
+	// and find the node
+	return query(2 * node, tl, tm, l, r)
+		+ query(2 * node + 1, tm + 1, tr, l, r);
+}
+
+// Driver code
+int main()
+{
+	int n = 6;
+	A = { 0, 1, 3, 5, -2, 3 };
+
+	// Create a segment tree of size 4*n
+	ST.resize(4 * n);
+
+	// Build a segment tree
+	build(1, 0, n - 1);
+	cout << "Sum of values in range 0-4 are: "
+		<< query(1, 0, n - 1, 0, 4) << "\n";
+
+	// Update the value at idx = 1 by
+	// 100 thus becoming 101
+	update(1, 0, n - 1, 1, 100);
+	cout << "Value at index 1 increased by 100\n";
+	cout << "sum of value in range 1-3 are: "
+		<< query(1, 0, n - 1, 1, 3) << "\n";
+
+	return 0;
+}