move to medium

coding_interviews/leetcode/medium/merge-nodes-in-between-zeros/merge-nodes-in-between-zeros.js

@@ -0,0 +1,37 @@
+export class ListNode {
+  constructor(val, next) {
+    this.val = val === undefined ? 0 : val;
+    this.next = next === undefined ? null : next;
+  }
+}
+
+export function mergeNodes(head) {
+  let nonZeroHead;
+  let node;
+  let nextNode;
+  let currentNode = head.next;
+  let valueSum = 0;
+  let gotFirstNode = false;
+
+  while (currentNode) {
+    valueSum += currentNode.val;
+
+    if (currentNode.val === 0) {
+      nextNode = new ListNode(valueSum);
+      valueSum = 0;
+
+      if (gotFirstNode) {
+        node.next = nextNode;
+        node = node.next;
+      } else {
+        node = nextNode;
+        nonZeroHead = nextNode;
+        gotFirstNode = true;
+      }
+    }
+
+    currentNode = currentNode.next;
+  }
+
+  return nonZeroHead;
+}

coding_interviews/leetcode/medium/merge-nodes-in-between-zeros/tests/merge-nodes-in-between-zeros.test.js

@@ -0,0 +1,30 @@
+import { describe, it, expect } from 'vitest';
+import { ListNode, mergeNodes } from '../merge-nodes-in-between-zeros';
+
+function buildList(nums, initValue = 0) {
+  let head = new ListNode(initValue);
+  let node = head;
+  let nextNode;
+
+  for (let i = 1; i < nums.length; i++) {
+    nextNode = new ListNode(nums[i]);
+    node.next = nextNode;
+    node = node.next;
+  }
+
+  return head;
+}
+
+describe('mergeNodes', () => {
+  it('removes zeros and merges nodes', () => {
+    const head = buildList([0, 3, 1, 0, 4, 5, 2, 0]);
+    const result = buildList([4, 11], 4);
+    expect(mergeNodes(head)).toEqual(result);
+  });
+
+  it('removes zeros and merges nodes', () => {
+    const head = buildList([0, 1, 0, 3, 0, 2, 2, 0]);
+    const result = buildList([1, 3, 4], 1);
+    expect(mergeNodes(head)).toEqual(result);
+  });
+});