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algorithmzuoalgorithmzuo
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modify code
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6 files changed

+255
-171
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‎src/class044/Code01_TrieTree.java‎

Lines changed: 57 additions & 90 deletions
Original file line numberDiff line numberDiff line change
@@ -1,116 +1,83 @@
11
package class044;
22

3-
// 用固定数组实现前缀树，空间使用是静态的，路径是数组结构
4-
// 测试链接 : https://www.nowcoder.com/practice/7f8a8553ddbf4eaab749ec988726702b
5-
// 请同学们务必参考如下代码中关于输入、输出的处理
6-
// 这是输入输出处理效率很高的写法
7-
// 提交以下的code，提交时请把类名改成"Main"，可以直接通过
8-
9-
import java.io.BufferedReader;
10-
import java.io.IOException;
11-
import java.io.InputStreamReader;
12-
import java.io.OutputStreamWriter;
13-
import java.io.PrintWriter;
14-
import java.util.Arrays;
15-
3+
// 用类描述实现前缀树，路径是数组结构
4+
// 测试链接 : https://leetcode.cn/problems/implement-trie-ii-prefix-tree/
165
public class Code01_TrieTree {
176

18-
public static int MAXN = 150001;
19-
20-
public static int[][] tree = new int[MAXN][26];
7+
class Trie {
218

22-
public static int[] end = new int[MAXN];
9+
class TrieNode {
10+
public int pass;
11+
public int end;
12+
public TrieNode[] nexts;
2313

24-
public static int[] pass = new int[MAXN];
14+
public TrieNode() {
15+
pass = 0;
16+
end = 0;
17+
nexts = new TrieNode[26];
18+
}
19+
}
2520

26-
public static int cnt;
21+
private TrieNode root;
2722

28-
public static void insert(String word) {
29-
int cur = 1;
30-
pass[cur]++;
31-
for (int i = 0, path; i < word.length(); i++) {
32-
path = word.charAt(i) - 'a';
33-
if (tree[cur][path] == 0) {
34-
tree[cur][path] = ++cnt;
35-
}
36-
cur = tree[cur][path];
37-
pass[cur]++;
23+
public Trie() {
24+
root = new TrieNode();
3825
}
39-
end[cur]++;
40-
}
4126

42-
public static void delete(String word) {
43-
if (search(word)) {
44-
int cur = 1;
45-
for (int i = 0, path; i < word.length(); i++) {
46-
path = word.charAt(i) - 'a';
47-
if (--pass[tree[cur][path]] == 0) {
48-
tree[cur][path] = 0;
49-
return;
27+
public void insert(String word) {
28+
TrieNode node = root;
29+
node.pass++;
30+
for (int i = 0, path; i < word.length(); i++) { // 从左往右遍历字符
31+
path = word.charAt(i) - 'a'; // 由字符，对应成走向哪条路
32+
if (node.nexts[path] == null) {
33+
node.nexts[path] = new TrieNode();
5034
}
51-
cur = tree[cur][path];
35+
node = node.nexts[path];
36+
node.pass++;
5237
}
53-
end[cur]--;
38+
node.end++;
5439
}
55-
}
5640

57-
public static boolean search(String word) {
58-
int cur = 1;
59-
for (int i = 0, path; i < word.length(); i++) {
60-
path = word.charAt(i) - 'a';
61-
if (tree[cur][path] == 0) {
62-
return false;
41+
public void erase(String word) {
42+
if (countWordsEqualTo(word) > 0) {
43+
TrieNode node = root;
44+
node.pass--;
45+
for (int i = 0, path; i < word.length(); i++) {
46+
path = word.charAt(i) - 'a';
47+
if (--node.nexts[path].pass == 0) {
48+
node.nexts[path] = null;
49+
return;
50+
}
51+
node = node.nexts[path];
52+
}
53+
node.end--;
6354
}
64-
cur = tree[cur][path];
6555
}
66-
return end[cur] > 0;
67-
}
6856

69-
public static int prefixNumber(String pre) {
70-
int cur = 1;
71-
for (int i = 0, path; i < pre.length(); i++) {
72-
path = pre.charAt(i) - 'a';
73-
if (tree[cur][path] == 0) {
74-
return 0;
57+
public int countWordsEqualTo(String word) {
58+
TrieNode node = root;
59+
for (int i = 0, path; i < word.length(); i++) {
60+
path = word.charAt(i) - 'a';
61+
if (node.nexts[path] == null) {
62+
return 0;
63+
}
64+
node = node.nexts[path];
7565
}
76-
cur = tree[cur][path];
66+
return node.end;
7767
}
78-
return pass[cur];
79-
}
80-
81-
public static int m, op;
82-
83-
public static String[] splits;
8468

85-
public static void main(String[] args) throws IOException {
86-
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
87-
PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
88-
String line = null;
89-
while ((line = in.readLine()) != null) {
90-
cnt = 1;
91-
m = Integer.valueOf(line);
92-
for (int i = 1; i <= m; i++) {
93-
splits = in.readLine().split(" ");
94-
op = Integer.valueOf(splits[0]);
95-
if (op == 1) {
96-
insert(splits[1]);
97-
} else if (op == 2) {
98-
delete(splits[1]);
99-
} else if (op == 3) {
100-
out.println(search(splits[1]) ? "YES" : "NO");
101-
} else if (op == 4) {
102-
out.println(prefixNumber(splits[1]));
69+
public int countWordsStartingWith(String pre) {
70+
TrieNode node = root;
71+
for (int i = 0, path; i < pre.length(); i++) {
72+
path = pre.charAt(i) - 'a';
73+
if (node.nexts[path] == null) {
74+
return 0;
10375
}
76+
node = node.nexts[path];
10477
}
105-
for (int i = 1; i <= cnt; i++) {
106-
Arrays.fill(tree[i], 0);
107-
end[i] = 0;
108-
pass[i] = 0;
109-
}
78+
return node.pass;
11079
}
111-
out.flush();
112-
in.close();
113-
out.close();
80+
11481
}
11582

11683
}

‎src/class044/Code02_TrieTree.java‎

Lines changed: 21 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
11
package class044;
22

3-
// 用类描述实现前缀树，路径是数组结构
3+
import java.util.HashMap;
4+
5+
// 用类描述实现前缀树，路径是哈希表结构
46
// 测试链接 : https://leetcode.cn/problems/implement-trie-ii-prefix-tree/
57
public class Code02_TrieTree {
68

@@ -9,12 +11,12 @@ class Trie {
911
class TrieNode {
1012
public int pass;
1113
public int end;
12-
public TrieNode[] nexts;
14+
HashMap<Integer, TrieNode> nexts;
1315

1416
public TrieNode() {
1517
pass = 0;
1618
end = 0;
17-
nexts = new TrieNode[26];
19+
nexts = new HashMap<>();
1820
}
1921
}
2022

@@ -28,11 +30,11 @@ public void insert(String word) {
2830
TrieNode node = root;
2931
node.pass++;
3032
for (int i = 0, path; i < word.length(); i++) { // 从左往右遍历字符
31-
path = word.charAt(i) - 'a'; // 由字符，对应成走向哪条路
32-
if (node.nexts[path] == null) {
33-
node.nexts[path] = new TrieNode();
33+
path = word.charAt(i);
34+
if (!node.nexts.containsKey(path)) {
35+
node.nexts.put(path, new TrieNode());
3436
}
35-
node = node.nexts[path];
37+
node = node.nexts.get(path);
3638
node.pass++;
3739
}
3840
node.end++;
@@ -41,14 +43,16 @@ public void insert(String word) {
4143
public void erase(String word) {
4244
if (countWordsEqualTo(word) > 0) {
4345
TrieNode node = root;
46+
TrieNode next;
4447
node.pass--;
4548
for (int i = 0, path; i < word.length(); i++) {
46-
path = word.charAt(i) - 'a';
47-
if (--node.nexts[path].pass == 0) {
48-
node.nexts[path] = null;
49+
path = word.charAt(i);
50+
next = node.nexts.get(path);
51+
if (--next.pass == 0) {
52+
node.nexts.remove(path);
4953
return;
5054
}
51-
node = node.nexts[path];
55+
node = next;
5256
}
5357
node.end--;
5458
}
@@ -57,23 +61,23 @@ public void erase(String word) {
5761
public int countWordsEqualTo(String word) {
5862
TrieNode node = root;
5963
for (int i = 0, path; i < word.length(); i++) {
60-
path = word.charAt(i) - 'a';
61-
if (node.nexts[path] == null) {
64+
path = word.charAt(i);
65+
if (!node.nexts.containsKey(path)) {
6266
return 0;
6367
}
64-
node = node.nexts[path];
68+
node = node.nexts.get(path);
6569
}
6670
return node.end;
6771
}
6872

6973
public int countWordsStartingWith(String pre) {
7074
TrieNode node = root;
7175
for (int i = 0, path; i < pre.length(); i++) {
72-
path = pre.charAt(i) - 'a';
73-
if (node.nexts[path] == null) {
76+
path = pre.charAt(i);
77+
if (!node.nexts.containsKey(path)) {
7478
return 0;
7579
}
76-
node = node.nexts[path];
80+
node = node.nexts.get(path);
7781
}
7882
return node.pass;
7983
}

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