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| 1 | +/** |
| 2 | + * 单链表的常见操作包括 |
| 3 | + * 链表反转 |
| 4 | + * 链表中环的检测 |
| 5 | + * 有序链表的合并 |
| 6 | + * 删除链表倒数第n个节点 |
| 7 | + * 链表中间节点 |
| 8 | + */ |
| 9 | +class LinkedListAlog { |
| 10 | + /** |
| 11 | + * 反转链表,依次将节点插入到头部 |
| 12 | + * @param list |
| 13 | + */ |
| 14 | + public static reverse<T>(list: SingleNode<T>): SingleNode<T> | null { |
| 15 | + let currentNode: SingleNode<T> | null = list |
| 16 | + let prevNode = null |
| 17 | + while (currentNode) { |
| 18 | + const nextNode: SingleNode<T> | null = currentNode.next |
| 19 | + currentNode.next = prevNode |
| 20 | + prevNode = currentNode |
| 21 | + currentNode = nextNode |
| 22 | + } |
| 23 | + return prevNode |
| 24 | + } |
| 25 | + |
| 26 | + /** |
| 27 | + * 通过快慢指针来检测是否为一个环 |
| 28 | + * @param list |
| 29 | + */ |
| 30 | + public static checkCircle<T>(list: SingleNode<T>): boolean { |
| 31 | + if (!list) return false |
| 32 | + let fast: SingleNode<T> | null = list.next |
| 33 | + let slow: SingleNode<T> | null = list |
| 34 | + while (fast && fast.next) { |
| 35 | + fast = fast.next.next |
| 36 | + slow = slow!!.next |
| 37 | + if (fast === slow) return true |
| 38 | + } |
| 39 | + return false |
| 40 | + } |
| 41 | + |
| 42 | + /** |
| 43 | + * 倒序删除节点 |
| 44 | + * @param list |
| 45 | + * @param index |
| 46 | + */ |
| 47 | + public static removeFromEnd<T>(list: SingleNode<T>, index: number): SingleNode<T> | null { |
| 48 | + // 如果是个环,就没必要找了 |
| 49 | + if (this.checkCircle(list)) return list |
| 50 | + let newNode = this.reverse(list) |
| 51 | + let preNode = null |
| 52 | + let pos = 0 |
| 53 | + while (newNode && pos !== index) { |
| 54 | + newNode = newNode.next |
| 55 | + pos++ |
| 56 | + preNode = newNode |
| 57 | + } |
| 58 | + if (!newNode) return null |
| 59 | + if (preNode) { |
| 60 | + preNode.next = newNode.next |
| 61 | + } |
| 62 | + return this.reverse(newNode) |
| 63 | + } |
| 64 | + |
| 65 | + public static findMidNode<T>(list: SingleNode<T>): SingleNode<T> | null { |
| 66 | + if (!list) return null |
| 67 | + let fast = list.next |
| 68 | + let slow = list |
| 69 | + while (fast && fast.next) { |
| 70 | + fast = fast.next.next |
| 71 | + slow = slow.next!! |
| 72 | + } |
| 73 | + return slow |
| 74 | + } |
| 75 | + |
| 76 | + /** |
| 77 | + * 有序链表的合并,根据不同的值进行插入 |
| 78 | + * @param a |
| 79 | + * @param b |
| 80 | + */ |
| 81 | + public static mergeSortedLists<T>(a: SingleNode<T>, b: SingleNode<T>): SingleNode<T> | null { |
| 82 | + if (!a || !b) return a ? a : b |
| 83 | + let p: SingleNode<T> | null = a |
| 84 | + let q: SingleNode<T> | null = b |
| 85 | + // 新链表的头部指针 |
| 86 | + let newList: SingleNode<T> | null = null |
| 87 | + if (p.value < q.value) { |
| 88 | + newList = p |
| 89 | + p = p.next |
| 90 | + } else { |
| 91 | + newList = q |
| 92 | + q = q.next |
| 93 | + } |
| 94 | + let currNode = newList |
| 95 | + while (p && q) { |
| 96 | + if (p.value < q.value) { |
| 97 | + currNode.next = p |
| 98 | + p = p.next |
| 99 | + } else { |
| 100 | + currNode.next = q |
| 101 | + q = q.next |
| 102 | + } |
| 103 | + currNode = currNode.next |
| 104 | + } |
| 105 | + if (p) { |
| 106 | + currNode.next = p |
| 107 | + } else { |
| 108 | + currNode.next = q |
| 109 | + } |
| 110 | + return newList |
| 111 | + } |
| 112 | +} |
| 113 | + |
| 114 | +class SingleNode<T> { |
| 115 | + public value: T |
| 116 | + public next: SingleNode<T> | null |
| 117 | + |
| 118 | + constructor(value: T, next: SingleNode<T> | null = null) { |
| 119 | + this.value = value |
| 120 | + this.next = next |
| 121 | + } |
| 122 | +} |
| 123 | + |
| 124 | + |
| 125 | +const node1 = new SingleNode(1) |
| 126 | +node1.next = new SingleNode(3) |
| 127 | +node1.next.next = new SingleNode(5) |
| 128 | + |
| 129 | +const node2 = new SingleNode(2) |
| 130 | +node2.next = new SingleNode(7) |
| 131 | +node2.next.next = new SingleNode(8) |
| 132 | +node2.next.next.next = new SingleNode(10) |
| 133 | + |
| 134 | +console.log(LinkedListAlog.findMidNode(node1)) |
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