Create Segment Tree.java

Author: vishantrathi

Diff for: Trees/Segment Tree.java

@@ -0,0 +1,49 @@
+class SegmentTree {
+    constructor(arr) {
+        this.n = arr.length;
+        this.tree = new Array(2 * this.n);
+        this.build(arr);
+    }
+
+    build(arr) {
+        for (let i = 0; i < this.n; i++) {
+            this.tree[this.n + i] = arr[i];
+        }
+        for (let i = this.n - 1; i > 0; --i) {
+            this.tree[i] = this.tree[i * 2] + this.tree[i * 2 + 1];
+        }
+    }
+
+    update(index, value) {
+        index += this.n;
+        this.tree[index] = value;
+        while (index > 1) {
+            index >>= 1;
+            this.tree[index] = this.tree[index * 2] + this.tree[index * 2 + 1];
+        }
+    }
+
+    query(left, right) {
+        let res = 0;
+        left += this.n;
+        right += this.n;
+        while (left < right) {
+            if (left & 1) {
+                res += this.tree[left++];
+            }
+            if (right & 1) {
+                res += this.tree[--right];
+            }
+            left >>= 1;
+            right >>= 1;
+        }
+        return res;
+    }
+}
+
+// Example usage
+let arr = [1, 3, 5, 7, 9, 11];
+let segTree = new SegmentTree(arr);
+console.log(segTree.query(1, 3)); // Output: 8
+segTree.update(1, 10);
+console.log(segTree.query(1, 3)); // Output: 15