數據結構與算法(JAVA版)5_1:前綴樹Part1:插入範圍限定在26個小寫字母

package com.inspire.chapter5;

public class TrieTree {

	public static class Node1 {
		public int pass;
		public int end;
		public Node1[] nexts;

		public Node1() {
			pass = 0;
			end = 0;
			/*
			 * 0	a
			 * 1	b
			 * ..	..
			 * 25	z
			 * nexts[i]=null	i方向的路不存在
			 * nexts[i]!=null	i方向的路存在
			 */
			nexts = new Node1[26];
		}
	}

	public static class Trie1 {
		private Node1 root;

		public Trie1() {
			root = new Node1();
		}

		// 插入字符串
		public void insert(String word) {
			if (word == null) {
				return;
			}
			char[] str = word.toCharArray();
			Node1 node = root;
			node.pass++;
			int path = 0;
			for (int i = 0; i < str.length; i++) {// 從左往右遍歷字符
				path = str[i] - 'a';// 由字符對應成走那條路
				if (node.nexts[path] == null) {
					node.nexts[path] = new Node1();
				}
				node = node.nexts[path];
				node.pass++;
			}
			node.end++;
		}

		// 查詢指定字符串出現的次數
		public int search(String word) {
			if (word == null) {
				return 0;
			}
			char[] str = word.toCharArray();
			Node1 node = root;
			int index = 0;
			for (int i = 0; i < str.length; i++) {
				index = str[i] - 'a';
				if (node.nexts[index] == null) {
					return 0;
				}
				node = node.nexts[index];
			}
			return node.end;
		}

		// 所有加入的字符串中，有幾個是以pre這個字符串作爲前綴的
		public int prefixNumber(String pre) {
			if (pre == null) {
				return 0;
			}
			char[] str = pre.toCharArray();
			Node1 node = root;
			int index = 0;
			for (int i = 0; i < str.length; i++) {
				index = str[i] - 'a';
				if (node.nexts[index] == null) {
					return 0;
				}
				node = node.nexts[index];
			}
			return node.pass;
		}

		//刪除指定字符串
		public void delete(String word) {
			if (search(word) != 0) {
				char[] str = word.toCharArray();
				Node1 node = root;
				node.pass--;
				int path = 0;
				for (int i = 0; i < str.length; i++) {
					path = str[i] - 'a';
					if (--node.nexts[path].pass == 0) {
						node.nexts[path] = null;
						return;
					}
					node = node.nexts[path];
				}
				node.end--;
			}
		}

	}

	public static void main(String[] args) {
		Trie1 trie1=new Trie1();
		String[] str={"abc","abcd","dfg","ddd","abc"};
		for(int i=0;i<str.length;i++){
			trie1.insert(str[i]);
		}
		trie1.delete("abc");
		int n=trie1.search("abc");
		System.out.println(n);
	}

}