Added lazySegmentTree.cpp

Lazy Propagation in Segment Tree

Author: Indrahas

Diff for: lazySegmentTree.cpp

@@ -0,0 +1,80 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+
+#define inf             1e18
+
+
+int lazy[10000] = {0};
+void lazyUpdate(int tree[], int s, int e, int l, int r, int val , int index) {
+	if (lazy[index] != 0) {
+		tree[index] += lazy[index];
+		if (e != s) {
+			lazy[2 * index] += lazy[index];
+			lazy[2 * index + 1] += lazy[index];
+		}
+		lazy[index] = 0;
+	}
+
+	if (s > r or e < l) return;
+
+	if (s >= l and e <= r) {
+		tree[index] += val;
+		if (e != s) {
+			lazy[2 * index] += val;
+			lazy[2 * index + 1] += val;
+		}
+		return;
+	}
+
+	int mid = (s + e) / 2;
+	lazyUpdate(tree, s, mid, l, r, val, 2 * index);
+	lazyUpdate(tree, mid + 1, e, l, r, val, 2 * index + 1);
+	tree[index] = min(tree[2 * index], tree[2 * index + 1]);
+	return;
+}
+
+int lazyQuery(int tree[], int s, int e, int l, int r, int index) {
+	if (lazy[index] != 0) {
+		tree[index] += lazy[index];
+		if (e != s) {
+			lazy[2 * index] = lazy[index];
+			lazy[2 * index + 1] = lazy[index];
+		}
+		lazy[index] = 0;
+	}
+
+	if (s > r or e < l) return inf;
+	if (s >= l and e <= r) return tree[index];
+
+	int mid = (s + e) / 2;
+	int left = lazyQuery(tree, s, mid, l, r, 2 * index);
+	int right = lazyQuery(tree, mid + 1, e, l, r, 2 * index + 1);
+	return min(left, right);
+
+
+}
+
+void build(int a[], int tree[], int s, int e, int index) {
+	if (s == e) {
+		tree[index] = a[e];
+		return;
+	}
+	int mid = (s + e) / 2;
+	build(a, tree, s, mid, 2 * index);
+	build(a, tree, mid + 1, e, 2 * index + 1);
+	tree[index] = min(tree[2 * index], tree[2 * index + 1]);
+	return;
+}
+
+
+int32_t main()
+{
+    //An example of implementing this code
+	// int a[] = {1, 3, 2, -5, 6, 4};
+	// int n = sizeof(a) / sizeof(int);
+	// int tree[4 * n + 1];
+	// build(a, tree, 0, n - 1, 1);
+	// lazyUpdate(tree, 0, n - 1, 0, 2, 10, 1);
+	// return 0;
+}