一款功能強大的視訊轉換工具
阿新 • • 發佈：2021-10-09
心之所向，素履以往 生如逆旅，一葦以航import java.util.ArrayList; public class SkipListMap { // 跳錶的節點定義 public static class SkipListNode<K extends Comparable<K>, V> { public K key; public V val; // 0 nextNodes.get(0) // 1 nextNodes.get(1) // i nextNodes.get(i) // nextNodes.size() public ArrayList<SkipListNode<K, V>> nextNodes; public SkipListNode(K k, V v) { key = k; val = v; // node 7層指標 // nextNodes.add(null) // nextNodes.add(null) // nextNodes.add(null) // nextNodes.add(null) // nextNodes.add(null) // nextNodes.add(null) // nextNodes.add(null) nextNodes = new ArrayList<SkipListNode<K, V>>(); } // 遍歷的時候，如果是往右遍歷到的null(next == null), 遍歷結束 // 頭(null), 頭節點的null，認為最小 // node -> 頭，node(null, "") node.isKeyLess(!null) true // node裡面的key是否比otherKey小，true，不是false public boolean isKeyLess(K otherKey) { // otherKey == null -> false return otherKey != null && (key == null || key.compareTo(otherKey) < 0); } public boolean isKeyEqual(K otherKey) { return (key == null && otherKey == null) || (key != null && otherKey != null && key.compareTo(otherKey) == 0); } } public static class SkipListMap<K extends Comparable<K>, V> { private static final double PROBABILITY = 0.5; // < 0.5 繼續做，>=0.5 停 private SkipListNode<K, V> head; private int size; private int maxLevel; public SkipListMap() { head = new SkipListNode<K, V>(null, null); head.nextNodes.add(null); size = 0; maxLevel = 0; } // 從最高層開始，一路找下去， // 最終，找到第0層的<key的最右的節點 private SkipListNode<K, V> mostRightLessNodeInTree(K key) { if (key == null) { return null; } int level = maxLevel; SkipListNode<K, V> cur = head; while (level >= 0) { // 從上層跳下層 // cur level -> level-1 cur = mostRightLessNodeInLevel(key, cur, level--); } return cur; } // 在level層裡，如何往右移動 // 現在來到的節點是cur，來到了cur的level層，在level層上，找到<key最後一個節點並返回 private SkipListNode<K, V> mostRightLessNodeInLevel(K key, SkipListNode<K, V> cur, int level) { SkipListNode<K, V> next = cur.nextNodes.get(level); while (next != null && next.isKeyLess(key)) { cur = next; next = cur.nextNodes.get(level); } return cur; } public boolean containsKey(K key) { if (key == null) { return false; } SkipListNode<K, V> less = mostRightLessNodeInTree(key); SkipListNode<K, V> next = less.nextNodes.get(0); return next != null && next.isKeyEqual(key); } public void put(K key, V value) { if (key == null) { return; } SkipListNode<K, V> less = mostRightLessNodeInTree(key); SkipListNode<K, V> find = less.nextNodes.get(0); if (find != null && find.isKeyEqual(key)) { find.val = value; } else { size++; int newNodeLevel = 0; while (Math.random() < PROBABILITY) { newNodeLevel++; } while (newNodeLevel > maxLevel) { head.nextNodes.add(null); maxLevel++; } SkipListNode<K, V> newNode = new SkipListNode<K, V>(key, value); for (int i = 0; i <= newNodeLevel; i++) { newNode.nextNodes.add(null); } int level = maxLevel; SkipListNode<K, V> pre = head; while (level >= 0) { pre = mostRightLessNodeInLevel(key, pre, level); if (level <= newNodeLevel) { newNode.nextNodes.set(level, pre.nextNodes.get(level)); pre.nextNodes.set(level, newNode); } level--; } } } public V get(K key) { if (key == null) { return null; } SkipListNode<K, V> less = mostRightLessNodeInTree(key); SkipListNode<K, V> next = less.nextNodes.get(0); return next != null && next.isKeyEqual(key) ? next.val : null; } public void remove(K key) { if (containsKey(key)) { size--; int level = maxLevel; SkipListNode<K, V> pre = head; while (level >= 0) { pre = mostRightLessNodeInLevel(key, pre, level); SkipListNode<K, V> next = pre.nextNodes.get(level); // 1）在這一層中，pre下一個就是key // 2）在這一層中，pre的下一個key是>要刪除key if (next != null && next.isKeyEqual(key)) { // free delete node memory -> C++ // level : pre -> next(key) -> ... pre.nextNodes.set(level, next.nextNodes.get(level)); } // 在level層只有一個節點了，就是預設節點head if (level != 0 && pre == head && pre.nextNodes.get(level) == null) { head.nextNodes.remove(level); maxLevel--; } level--; } } } public K firstKey() { return head.nextNodes.get(0) != null ? head.nextNodes.get(0).key : null; } public K lastKey() { int level = maxLevel; SkipListNode<K, V> cur = head; while (level >= 0) { SkipListNode<K, V> next = cur.nextNodes.get(level); while (next != null) { cur = next; next = cur.nextNodes.get(level); } level--; } return cur.key; } public K ceillingKey(K key) { if (key == null) { return null; } SkipListNode<K, V> less = mostRightLessNodeInTree(key); SkipListNode<K, V> next = less.nextNodes.get(0); return next != null ? next.key : null; } public K floorKey(K key) { if (key == null) { return null; } SkipListNode<K, V> less = mostRightLessNodeInTree(key); SkipListNode<K, V> next = less.nextNodes.get(0); return next != null && next.isKeyEqual(key) ? next.key : less.key; } public int size() { return size; } } // for test public static void printAll(SkipListMap<String, String> obj) { for (int i = obj.maxLevel; i >= 0; i--) { System.out.print("Level " + i + " : "); SkipListNode<String, String> cur = obj.head; while (cur.nextNodes.get(i) != null) { SkipListNode<String, String> next = cur.nextNodes.get(i); System.out.print("(" + next.key + " , " + next.val + ") "); cur = next; } System.out.println(); } } public static void main(String[] args) { SkipListMap<String, String> test = new SkipListMap<>(); printAll(test); System.out.println("======================"); test.put("A", "10"); printAll(test); System.out.println("======================"); test.remove("A"); printAll(test); System.out.println("======================"); test.put("E", "E"); test.put("B", "B"); test.put("A", "A"); test.put("F", "F"); test.put("C", "C"); test.put("D", "D"); printAll(test); System.out.println("======================"); System.out.println(test.containsKey("B")); System.out.println(test.containsKey("Z")); System.out.println(test.firstKey()); System.out.println(test.lastKey()); System.out.println(test.floorKey("D")); System.out.println(test.ceillingKey("D")); System.out.println("======================"); test.remove("D"); printAll(test); System.out.println("======================"); System.out.println(test.floorKey("D")); System.out.println(test.ceillingKey("D")); } }