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Commit 9457a6e

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clean code
1 parent 0934c1c commit 9457a6e

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15 files changed

+219
-217
lines changed

15 files changed

+219
-217
lines changed

‎leetcode/leetcode-02/src/main/java/Solution128.java

Lines changed: 11 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -3,22 +3,21 @@
33

44
public class Solution128 {
55
public int longestConsecutive(int[] nums) {
6-
Set<Integer> hashSet = new HashSet<>();
7-
for (int num : nums) {
8-
hashSet.add(num);
6+
Set<Integer> set = new HashSet<>();
7+
for (int v : nums) {
8+
set.add(v);
99
}
1010

11-
int max = 0;
12-
for (int num : nums) {
13-
if (!hashSet.contains(num - 1)) {
14-
int cnt = 0;
15-
while (hashSet.contains(num + cnt)) {
16-
cnt++;
17-
}
18-
max = Math.max(max, cnt);
11+
int ans = 0;
12+
for (int v : set) {
13+
if (set.contains(v - 1)) continue;
14+
int cnt = 0;
15+
while (set.contains(v + cnt)) {
16+
cnt++;
1917
}
18+
ans = Math.max(ans, cnt);
2019
}
21-
return max;
20+
return ans;
2221
}
2322
}
2423
/*

‎leetcode/leetcode-02/src/main/java/Solution131.java

Lines changed: 30 additions & 43 deletions
Original file line numberDiff line numberDiff line change
@@ -3,59 +3,46 @@
33
import java.util.List;
44

55
public class Solution131 {
6-
/**
7-
* 剑指 Offer II 086. 分割回文子字符串
8-
* https://leetcode.cn/problems/M99OJA/
9-
*/
6+
// 剑指 Offer II 086. 分割回文子字符串
7+
// https://leetcode.cn/problems/M99OJA/
108
public String[][] partition(String s) {
11-
List<List<String>> resList = partition131(s);
12-
// List<List<String>> 转 String[][]
13-
int resM = resList.size();
14-
String[][] res = new String[resM][];
15-
for (int i = 0; i < resM; i++) {
16-
int resN = resList.get(i).size();
17-
res[i] = new String[resN];
18-
for (int j = 0; j < resN; j++) {
19-
res[i][j] = resList.get(i).get(j);
20-
}
21-
}
22-
return res;
9+
V1 sol = new V1();
10+
List<List<String>> res = sol.partition(s);
11+
return res.stream().map(row -> row.toArray(String[]::new)).toArray(String[][]::new);
2312
}
2413

25-
/**
26-
* 131. 分割回文串
27-
* https://leetcode.cn/problems/palindrome-partitioning/
28-
*/
29-
public List<List<String>> partition131(String s) {
30-
List<List<String>> resList = new ArrayList<>();
31-
helper(s, 0, new LinkedList<>(), resList);
32-
return resList;
33-
}
14+
static class V1 {
15+
String s;
16+
List<List<String>> ans;
3417

35-
private void helper(String s, int start, LinkedList<String> subStrings, List<List<String>> resList) {
36-
if (start == s.length()) {
37-
resList.add(new ArrayList<>(subStrings));
38-
return;
18+
public List<List<String>> partition(String s) {
19+
this.s = s;
20+
ans = new ArrayList<>();
21+
backtrack(0, new ArrayList<>());
22+
return ans;
3923
}
40-
for (int i = start; i < s.length(); i++) {
41-
if (isPal(s, start, i)) {
42-
subStrings.add(s.substring(start, i + 1));
43-
helper(s, i + 1, subStrings, resList);
44-
subStrings.removeLast();
45-
}
4624

25+
// 考虑 s[i] ~ s[n-1] 怎么分割
26+
private void backtrack(int i, List<String> path) {
27+
if (i == s.length()) {
28+
ans.add(new ArrayList<>(path));
29+
return;
30+
}
31+
for (int j = i; j < s.length(); j++) {
32+
if (isPal(i, j)) {
33+
path.add(s.substring(i, j + 1));
34+
backtrack(j + 1, path);
35+
path.removeLast();
36+
}
37+
}
4738
}
48-
}
4939

50-
private boolean isPal(String s, int start, int end) {
51-
while (start < end) {
52-
if (s.charAt(start) != s.charAt(end)) {
53-
return false;
40+
private boolean isPal(int l, int r) {
41+
while (l < r) {
42+
if (s.charAt(l++) != s.charAt(r--)) return false;
5443
}
55-
start++;
56-
end--;
44+
return true;
5745
}
58-
return true;
5946
}
6047
}
6148
/*

‎leetcode/leetcode-02/src/main/java/Solution132.java

Lines changed: 14 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -1,31 +1,29 @@
11
public class Solution132 {
2-
public int minCut(String s) {
3-
int len = s.length();
4-
boolean[][] isPal = new boolean[len][len];
5-
for (int i = 0; i < len; i++) {
2+
public int minCut(String S) {
3+
int n = S.length();
4+
char[] s = S.toCharArray();
5+
// 预处理
6+
boolean[][] isPal = new boolean[n][n];
7+
for (int i = 0; i < n; i++) {
68
for (int j = 0; j <= i; j++) {
7-
char ch1 = s.charAt(i);
8-
char ch2 = s.charAt(j);
9-
if (ch1 == ch2 && (i <= j + 1 || isPal[j + 1][i - 1])) {
9+
if (s[i] == s[j] && (i - 1 <= j || isPal[j + 1][i - 1])) {
1010
isPal[j][i] = true;
1111
}
1212
}
1313
}
14-
// dp
15-
int[] dp = new int[len];
16-
for (int i = 0; i < len; i++) {
17-
if (isPal[0][i]) {
18-
dp[i] = 0;
19-
} else {
20-
dp[i] = i;
14+
// f[i] 表示从下标 0 到 i 的子字符串符合条件的最少分割次数,则问题解为 f[n-1]
15+
int[] f = new int[n];
16+
for (int i = 0; i < n; i++) {
17+
if (!isPal[0][i]) {
18+
f[i] = i;
2119
for (int j = 1; j <= i; j++) {
2220
if (isPal[j][i]) {
23-
dp[i] = Math.min(dp[i], dp[j - 1] + 1);
21+
f[i] = Math.min(f[i], f[j - 1] + 1);
2422
}
2523
}
2624
}
2725
}
28-
return dp[len - 1];
26+
return f[n - 1];
2927
}
3028
}
3129
/*

‎leetcode/leetcode-02/src/test/java/Solution131Tests.java

Lines changed: 7 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -4,15 +4,16 @@
44
import java.util.List;
55

66
public class Solution131Tests {
7-
private final Solution131 solution131 = new Solution131();
7+
private final Solution131.V1 solution131 = new Solution131.V1();
8+
private final Solution131 solutionLCR086 = new Solution131();
89

910
@Test
1011
public void example1() {
1112
String s = "aab";
1213
List<List<String>> expected = UtUtils.stringToStringList2("""
1314
[["a","a","b"],["aa","b"]]
1415
""");
15-
Assertions.assertEquals(expected, solution131.partition131(s));
16+
Assertions.assertEquals(expected, solution131.partition(s));
1617
}
1718

1819
@Test
@@ -21,7 +22,7 @@ public void example2() {
2122
List<List<String>> expected = UtUtils.stringToStringList2("""
2223
[["a"]]
2324
""");
24-
Assertions.assertEquals(expected, solution131.partition131(s));
25+
Assertions.assertEquals(expected, solution131.partition(s));
2526
}
2627

2728
// 剑指 Offer II 086. 分割回文子字符串
@@ -32,7 +33,7 @@ public void example1_2() {
3233
String[][] expected = UtUtils.stringToStrings2("""
3334
[["g","o","o","g","l","e"],["g","oo","g","l","e"],["goog","l","e"]]
3435
""");
35-
Assertions.assertArrayEquals(expected, solution131.partition(s));
36+
Assertions.assertArrayEquals(expected, solutionLCR086.partition(s));
3637
}
3738

3839
@Test
@@ -41,7 +42,7 @@ public void example2_2() {
4142
String[][] expected = UtUtils.stringToStrings2("""
4243
[["a","a","b"],["aa","b"]]
4344
""");
44-
Assertions.assertArrayEquals(expected, solution131.partition(s));
45+
Assertions.assertArrayEquals(expected, solutionLCR086.partition(s));
4546
}
4647

4748
@Test
@@ -50,6 +51,6 @@ public void example3_2() {
5051
String[][] expected = UtUtils.stringToStrings2("""
5152
[["a"]]
5253
""");
53-
Assertions.assertArrayEquals(expected, solution131.partition(s));
54+
Assertions.assertArrayEquals(expected, solutionLCR086.partition(s));
5455
}
5556
}
Lines changed: 22 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -1,27 +1,30 @@
1+
import java.util.ArrayList;
2+
import java.util.Collections;
3+
import java.util.List;
4+
15
public class Solution498 {
26
public int[] findDiagonalOrder(int[][] mat) {
37
int m = mat.length;
48
int n = mat[0].length;
59

6-
int[] ans = new int[m * n];
7-
int j = 0;
8-
for (int i = 0; i < m + n - 1; i++) {
9-
if (i % 2 == 1) {
10-
// 左上到右下
11-
int x = i < n ? 0 : i - n + 1;
12-
int y = i < n ? i : n - 1;
13-
while (x < m && y >= 0) {
14-
ans[j++] = mat[x++][y--];
15-
}
16-
} else {
17-
int x = i < m ? i : m - 1;
18-
int y = i < m ? 0 : i - m + 1;
19-
while (x >= 0 && y < n) {
20-
ans[j++] = mat[x--][y++];
21-
}
10+
List<Integer> ans = new ArrayList<>();
11+
// 共有 m+n-1 条(主/次)对角线,k 的范围 [1, m+n-1]
12+
// 主对角线(左上到右下) 令 k=i+j+1 左上角 k=1 右下角 k=m+n-1, j=k-i-1, i=k-j-1
13+
// 次对角线(右上到左下) 令 k=i-j+n 右上角 k=1 左下角 k=m+n-1, j=i-k+n, i=k+j-n
14+
for (int k = 1; k <= m + n - 1; k++) {
15+
int min_j = Math.max(k - 1 - (m - 1), 0);
16+
int max_j = Math.min(k - 1, n - 1);
17+
18+
List<Integer> a = new ArrayList<>();
19+
for (int j = min_j; j <= max_j; j++) {
20+
int i = k - j - 1;
21+
a.add(mat[i][j]);
2222
}
23+
24+
if (k % 2 == 0) Collections.reverse(a);
25+
ans.addAll(a);
2326
}
24-
return ans;
27+
return ans.stream().mapToInt(Integer::intValue).toArray();
2528
}
2629
}
2730
/*
@@ -38,4 +41,6 @@ public int[] findDiagonalOrder(int[][] mat) {
3841
3942
模拟。
4043
时间复杂度 O(mn)。
44+
相似题目: 3446. 按对角线进行矩阵排序
45+
https://leetcode.cn/problems/sort-matrix-by-diagonals/description/
4146
*/

‎leetcode/leetcode-21/src/main/java/Solution2012.java

Lines changed: 12 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,30 +1,30 @@
11
public class Solution2012 {
22
public int sumOfBeauties(int[] nums) {
3-
int len = nums.length;
4-
int res = 0;
5-
for (int i = 1; i <= len - 2; i++) {
3+
int n = nums.length;
4+
int ans = 0;
5+
for (int i = 1; i <= n - 2; i++) {
66
if (nums[i - 1] < nums[i] && nums[i] < nums[i + 1]) {
7-
res++;
7+
ans++;
88
}
99
}
1010
// leftMax[i] 表示 nums[0, i] 的最大值
11-
int[] leftMax = new int[len];
11+
int[] leftMax = new int[n];
1212
leftMax[0] = nums[0];
13-
for (int i = 1; i < len; i++) {
13+
for (int i = 1; i < n; i++) {
1414
leftMax[i] = Math.max(leftMax[i - 1], nums[i]);
1515
}
1616
// rightMin[i] 表示 nums[i, len-1] 的最小值
17-
int[] rightMin = new int[len];
18-
rightMin[len - 1] = nums[len - 1];
19-
for (int i = len - 2; i >= 0; i--) {
17+
int[] rightMin = new int[n];
18+
rightMin[n - 1] = nums[n - 1];
19+
for (int i = n - 2; i >= 0; i--) {
2020
rightMin[i] = Math.min(rightMin[i + 1], nums[i]);
2121
}
22-
for (int i = 1; i <= len - 2; i++) {
22+
for (int i = 1; i <= n - 2; i++) {
2323
if (leftMax[i - 1] < nums[i] && nums[i] < rightMin[i + 1]) {
24-
res++;
24+
ans++;
2525
}
2626
}
27-
return res;
27+
return ans;
2828
}
2929
}
3030
/*

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