ДЗ 1, Симиютин Борис, подгруппа 2 #11
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,144 @@ | ||
| package ru.spbau.mit; | ||
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| public class StringSetImpl implements StringSet { | ||
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| private int size; | ||
| private Node root; | ||
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| StringSetImpl() { | ||
| root = new Node('a'); | ||
| } | ||
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| @Override | ||
| public boolean add(String element) { | ||
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| if (contains(element)) { | ||
| return false; | ||
| } | ||
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| Node node = root; | ||
| for (char value : element.toCharArray()) { | ||
| Node child = node.getChild(value); | ||
| if (child == null) { | ||
| child = new Node(value); | ||
| child.parent = node; | ||
| node.addChild(child); | ||
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| } | ||
| node.howManyStartsWithPrefix++; | ||
| node = child; | ||
| } | ||
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| node.isFullWord = true; | ||
| node.howManyStartsWithPrefix++; | ||
| size++; | ||
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| return true; | ||
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| } | ||
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| private Node findLastNode(String element) { | ||
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| Node node = root; | ||
| for (char value : element.toCharArray()) { | ||
| Node child = node.getChild(value); | ||
| if (child == null) { | ||
| return null; | ||
| } | ||
| node = child; | ||
| } | ||
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| return node; | ||
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| } | ||
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| @Override | ||
| public boolean contains(String element) { | ||
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| Node node = findLastNode(element); | ||
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| return node != null && node.isFullWord; | ||
| } | ||
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| private int getIndexByChar(char value) { | ||
| final int asciiOffset = 65; | ||
| return value - asciiOffset; | ||
| } | ||
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| @Override | ||
| public boolean remove(String element) { | ||
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| if (!contains(element)) { | ||
| return false; | ||
| } | ||
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| Node lastNode = findLastNode(element); | ||
| lastNode.isFullWord = false; | ||
| lastNode.howManyStartsWithPrefix--; | ||
| size--; | ||
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| char[] array = element.toCharArray(); | ||
| Node parent = lastNode.parent; | ||
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| // decrement value on path to root | ||
| for (int i = element.length() - 1; i >= 0; i--) { | ||
| parent.howManyStartsWithPrefix--; | ||
| parent = parent.parent; | ||
| } | ||
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| // delete unused prefix | ||
| if (lastNode.numberOfChildren == 0) { | ||
| parent = lastNode.parent; | ||
| for (int i = element.length() - 1; i >= 0; i--) { | ||
| parent.numberOfChildren--; | ||
| parent.children[getIndexByChar(array[i])] = null; | ||
| if (parent.isFullWord || parent.numberOfChildren > 0) { | ||
| break; | ||
| } | ||
| parent = parent.parent; | ||
| } | ||
| } | ||
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| return true; | ||
| } | ||
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| @Override | ||
| public int size() { | ||
| return size; | ||
| } | ||
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| @Override | ||
| public int howManyStartsWithPrefix(String prefix) { | ||
| Node lastNode = findLastNode(prefix); | ||
| if (lastNode == null) { | ||
| return 0; | ||
| } | ||
| return lastNode.howManyStartsWithPrefix; | ||
| } | ||
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| class Node { | ||
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| private Node[] children; | ||
| private char value; | ||
| private int numberOfChildren; | ||
| private int howManyStartsWithPrefix; | ||
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Author
There was a problem hiding this comment. Действительно, они полностью друг друга дублируют, и от одного поля можно избавиться |
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| private boolean isFullWord; | ||
| private Node parent; | ||
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| Node(char value) { | ||
| final int sizeOfFrameInAscii = 58; | ||
| this.value = value; | ||
| this.children = new Node[sizeOfFrameInAscii]; | ||
| } | ||
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| Node getChild(char value) { | ||
| return children[getIndexByChar(value)]; | ||
| } | ||
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| void addChild(final Node newChild) { | ||
| children[getIndexByChar(newChild.value)] = newChild; | ||
| numberOfChildren++; | ||
| } | ||
| } | ||
| } | ||
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==
root.howMany...?There was a problem hiding this comment.
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Да, и size тут не нужен