fixes: #{}

Trees/FenwickTreeImplementation.js

@@ -0,0 +1,48 @@
+/*
+ * Author: Mohit Kumar
+ * Fedwick Tree Implementation in JavaScript
+ * Fedwick Tree Implementation for finding prefix sum.
+*/
+
+function constructFenwickTree(array, n) {
+ for (let i = 1; i <= n; i++) {
+ FeneickTree[i] = 0;
+ }
+ for (let i = 0; i < n; i++) {
+ updateFenwickTree(n, i, array[i]);
+ }
+}
+
+function updateFenwickTree(n, index, value) {
+ index = index + 1;
+ while (index <= n) {
+ FeneickTree[index] += value;
+ index += index & (-index);
+ }
+}
+
+function getPrefixSum(index) {
+ let currSum = 0;
+ index = index + 1;
+ while (index > 0) {
+ currSum += FeneickTree[index];
+ index -= index & (-index);
+ }
+
+ return currSum;
+}
+
+let MAX_VALUE = 1000;
+let FeneickTree = new Array(MAX_VALUE);
+let array = [3, 2, 0, 6, 5, -1, 2];
+
+let length = array.length;
+constructFenwickTree(array, length);
+
+getPrefixSum(6);
+array[2] += 6;
+updateFenwickTree(length, 2, 6);
+getPrefixSum(6);
+
+//Output1 : 17
+//Output2 : 23