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Commit c18d119

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jadestrongtrekhleb
authored andcommitted
fixed doubly-linked-list reverse method omit change node's previous (trekhleb#257)
1 parent 4e27a97 commit c18d119

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2 files changed

+30
-7
lines changed

2 files changed

+30
-7
lines changed

‎src/data-structures/doubly-linked-list/DoublyLinkedList.js‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -243,9 +243,11 @@ export default class DoublyLinkedList {
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while (currNode) {
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// Store next node.
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nextNode = currNode.next;
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prevNode = currNode.previous;
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// Change next node of the current node so it would link to previous node.
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currNode.next = prevNode;
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currNode.previous = nextNode;
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// Move prevNode and currNode nodes one step forward.
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prevNode = currNode;

‎src/data-structures/doubly-linked-list/__test__/DoublyLinkedList.test.js‎

Lines changed: 28 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -236,22 +236,43 @@ describe('DoublyLinkedList', () => {
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linkedList
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.append(1)
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.append(2)
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.append(3);
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.append(3)
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.append(4);
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expect(linkedList.toString()).toBe('1,2,3');
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expect(linkedList.toString()).toBe('1,2,3,4');
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expect(linkedList.head.value).toBe(1);
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expect(linkedList.tail.value).toBe(3);
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expect(linkedList.tail.value).toBe(4);
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// Reverse linked list.
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linkedList.reverse();
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expect(linkedList.toString()).toBe('3,2,1');
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expect(linkedList.head.value).toBe(3);
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expect(linkedList.toString()).toBe('4,3,2,1');
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expect(linkedList.head.previous).toBeNull();
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expect(linkedList.head.value).toBe(4);
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expect(linkedList.head.next.value).toBe(3);
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expect(linkedList.head.next.next.value).toBe(2);
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expect(linkedList.head.next.next.next.value).toBe(1);
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expect(linkedList.tail.next).toBeNull();
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expect(linkedList.tail.value).toBe(1);
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expect(linkedList.tail.previous.value).toBe(2);
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expect(linkedList.tail.previous.previous.value).toBe(3);
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expect(linkedList.tail.previous.previous.previous.value).toBe(4);
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// Reverse linked list back to initial state.
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linkedList.reverse();
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expect(linkedList.toString()).toBe('1,2,3');
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expect(linkedList.toString()).toBe('1,2,3,4');
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expect(linkedList.head.previous).toBeNull();
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expect(linkedList.head.value).toBe(1);
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expect(linkedList.tail.value).toBe(3);
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expect(linkedList.head.next.value).toBe(2);
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expect(linkedList.head.next.next.value).toBe(3);
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expect(linkedList.head.next.next.next.value).toBe(4);
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expect(linkedList.tail.next).toBeNull();
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expect(linkedList.tail.value).toBe(4);
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expect(linkedList.tail.previous.value).toBe(3);
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expect(linkedList.tail.previous.previous.value).toBe(2);
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expect(linkedList.tail.previous.previous.previous.value).toBe(1);
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});
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});

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