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Commit 98432fb

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clean code
1 parent b7c120f commit 98432fb

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24 files changed

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-171
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24 files changed

+215
-171
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‎leetcode/leetcode-01/src/main/java/Solution64.java

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -40,4 +40,6 @@ public int minPathSum(int[][] grid) {
4040
定义 dp[i][j] 为 i x j 矩阵中,路径上的数字总和为最小的值。
4141
相似题目: 剑指 Offer 47. 礼物的最大价值
4242
https://leetcode.cn/problems/li-wu-de-zui-da-jie-zhi-lcof/
43+
3603. 交替方向的最小路径代价 II
44+
https://leetcode.cn/problems/minimum-cost-path-with-alternating-directions-ii/description/
4345
*/

‎leetcode/leetcode-02/src/main/java/Solution135.java

Lines changed: 11 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1,32 +1,30 @@
11
public class Solution135 {
22
public int candy(int[] ratings) {
3-
int len = ratings.length;
3+
int n = ratings.length;
44

5-
// 左往右
6-
int[] left = new int[len];
7-
for (int i = 0; i < len; i++) {
8-
if (i > 0 && ratings[i] > ratings[i - 1]) {
5+
int[] left = new int[n];
6+
for (int i = 0; i < n; i++) {
7+
if (i - 1 >= 0 && ratings[i] > ratings[i - 1]) {
98
left[i] = left[i - 1] + 1;
109
} else {
1110
left[i] = 1;
1211
}
1312
}
1413

15-
// 右往左
16-
int[] right = new int[len];
17-
for (int i = len - 1; i >= 0; i--) {
18-
if (i + 1 < len && ratings[i] > ratings[i + 1]) {
14+
int[] right = new int[n];
15+
for (int i = n - 1; i >= 0; i--) {
16+
if (i + 1 < n && ratings[i] > ratings[i + 1]) {
1917
right[i] = right[i + 1] + 1;
2018
} else {
2119
right[i] = 1;
2220
}
2321
}
2422

25-
int sum = 0;
26-
for (int i = 0; i < len; i++) {
27-
sum += Math.max(left[i], right[i]);
23+
int ans = 0;
24+
for (int i = 0; i < n; i++) {
25+
ans += Math.max(left[i], right[i]);
2826
}
29-
return sum;
27+
return ans;
3028
}
3129
}
3230
/*

‎leetcode/leetcode-02/src/main/java/Solution188.java

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -45,4 +45,6 @@ private int dfs(int i, int j, int hold) {
4545
0 <= prices[i] <= 1000
4646
4747
状态机 DP
48+
相似题目: 3573. 买卖股票的最佳时机 V
49+
https://leetcode.cn/problems/best-time-to-buy-and-sell-stock-v/description/
4850
*/

‎leetcode/leetcode-06/src/main/java/Solution518.java

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -27,4 +27,6 @@ public int change(int amount, int[] coins) {
2727
完全背包 求方案数。
2828
相似题目: 322. 零钱兑换
2929
https://leetcode.cn/problems/coin-change/
30+
3592. 硬币面值还原
31+
https://leetcode.cn/problems/inverse-coin-change/description/
3032
*/

‎leetcode/leetcode-08/src/main/java/Solution780.java

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -24,4 +24,6 @@ public boolean reachingPoints(int sx, int sy, int tx, int ty) {
2424
即 点 (x, y) 恢复到 (x, y-x) 或者 (x-y, y)。由于点为正整数,因此只有一种逆向可能。
2525
时间复杂度 O(logn)
2626
空间复杂度 O(1)
27+
相似题目: 3609. 到达目标点的最小移动次数
28+
https://leetcode.cn/problems/minimum-moves-to-reach-target-in-grid/description/
2729
*/

‎leetcode/leetcode-10/src/main/java/Solution909.java

Lines changed: 11 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,18 @@
1-
import java.util.LinkedList;
1+
import java.util.ArrayDeque;
22
import java.util.Queue;
33

44
public class Solution909 {
55
public int snakesAndLadders(int[][] board) {
66
int n = board.length;
7-
Queue<Integer> queue = new LinkedList<>();
8-
queue.add(1);
9-
boolean[] visited = new boolean[n * n + 1];
10-
visited[1] = true;
7+
Queue<Integer> q = new ArrayDeque<>();
8+
q.add(1);
9+
boolean[] vis = new boolean[n * n + 1];
10+
vis[1] = true;
1111
int step = 0;
12-
while (!queue.isEmpty()) {
13-
int size = queue.size();
12+
while (!q.isEmpty()) {
13+
int size = q.size();
1414
for (int i = 0; i < size; i++) {
15-
int cur = queue.remove();
15+
int cur = q.remove();
1616
if (cur == n * n) {
1717
return step;
1818
}
@@ -26,9 +26,9 @@ public int snakesAndLadders(int[][] board) {
2626
if (board[rc[0]][rc[1]] != -1) {
2727
next = board[rc[0]][rc[1]];
2828
}
29-
if (!visited[next]) {
30-
visited[next] = true;
31-
queue.add(next);
29+
if (!vis[next]) {
30+
vis[next] = true;
31+
q.add(next);
3232
}
3333
}
3434
}

‎leetcode/leetcode-11/src/main/java/Solution1036.java

Lines changed: 19 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,12 @@
1+
import java.util.ArrayDeque;
12
import java.util.Arrays;
23
import java.util.HashSet;
34
import java.util.LinkedList;
45
import java.util.Queue;
56
import java.util.Set;
67

78
public class Solution1036 {
9+
private static final int[][] DIRECTIONS = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
810
private static final int M = 1000000;
911
private static final int N = 1000000;
1012

@@ -21,33 +23,32 @@ public boolean isEscapePossible(int[][] blocked, int[] source, int[] target) {
2123
}
2224

2325
private boolean bfs(int[] source, int[] target, Set<String> blockedSet) {
24-
int[][] direction = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
2526
// BFS
26-
Queue<int[]> queue = new LinkedList<>();
27-
Set<String> visitedSet = new HashSet<>();
28-
queue.add(source);
29-
visitedSet.add(source[0] + ":" + source[1]);
27+
Queue<int[]> q = new ArrayDeque<>();
28+
Set<String> vis = new HashSet<>();
29+
q.add(source);
30+
vis.add(source[0] + ":" + source[1]);
3031

31-
// blockedS 可以围住的最大个数
32-
int len = blockedSet.size();
33-
int max = len * (len - 1) / 2;
32+
// blockedSet 可以围住的最大个数
33+
int k = blockedSet.size();
34+
int max = k * (k - 1) / 2;
3435
int cnt = 0;
35-
while (!queue.isEmpty()) {
36-
int size = queue.size();
36+
while (!q.isEmpty()) {
37+
int size = q.size();
3738
cnt += size;
3839
for (int i = 0; i < size; i++) {
39-
int[] cur = queue.remove();
40+
int[] cur = q.remove();
4041
// 到达目标方格
4142
if (Arrays.equals(cur, target)) {
4243
return true;
4344
}
44-
for (int[] dir : direction) {
45-
int nextM = cur[0] + dir[0];
46-
int nextN = cur[1] + dir[1];
47-
if (nextM >= 0 && nextM < M && nextN >= 0 && nextN < N && !visitedSet.contains(nextM + ":" + nextN)
48-
&& !blockedSet.contains(nextM + ":" + nextN)) {
49-
visitedSet.add(nextM + ":" + nextN);
50-
queue.add(new int[]{nextM, nextN});
45+
for (int[] d : DIRECTIONS) {
46+
int nx = cur[0] + d[0];
47+
int ny = cur[1] + d[1];
48+
if (nx >= 0 && nx < M && ny >= 0 && ny < N && !vis.contains(nx + ":" + ny)
49+
&& !blockedSet.contains(nx + ":" + ny)) {
50+
vis.add(nx + ":" + ny);
51+
q.add(new int[]{nx, ny});
5152
}
5253
}
5354
}

‎leetcode/leetcode-11/src/main/java/Solution1061.java

Lines changed: 14 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -1,56 +1,43 @@
11
public class Solution1061 {
22
public String smallestEquivalentString(String s1, String s2, String baseStr) {
3-
int len = s1.length();
3+
int n = s1.length();
44

55
DSU dsu = new DSU(26);
6-
for (int i = 0; i < len; i++) {
6+
for (int i = 0; i < n; i++) {
77
int idx1 = s1.charAt(i) - 'a';
88
int idx2 = s2.charAt(i) - 'a';
99
dsu.union(idx1, idx2);
1010
}
1111

12-
StringBuilder stringBuilder = new StringBuilder();
12+
StringBuilder ans = new StringBuilder();
1313
for (char ch : baseStr.toCharArray()) {
1414
int idx = dsu.find(ch - 'a');
15-
stringBuilder.append((char) (idx + 'a'));
15+
ans.append((char) (idx + 'a'));
1616
}
17-
return stringBuilder.toString();
17+
return ans.toString();
1818
}
1919

20-
private static class DSU {
21-
// 父节点数组/祖先数组
20+
static class DSU {
2221
int[] fa;
2322

24-
// 初始化
2523
public DSU(int n) {
2624
fa = new int[n];
2725
for (int i = 0; i < n; i++) {
2826
fa[i] = i;
2927
}
3028
}
3129

32-
// 查找
33-
int find(int x) {
34-
// 路径压缩
35-
if (x != fa[x]) {
36-
fa[x] = find(fa[x]);
37-
}
38-
return fa[x];
30+
int find(int x) { // 查找
31+
return x == fa[x] ? fa[x] : (fa[x] = find(fa[x]));
3932
}
4033

41-
// 合并
42-
void union(int p, int q) {
43-
int rootP = find(p);
44-
int rootQ = find(q);
45-
if (rootP == rootQ) {
46-
return;
47-
}
34+
void union(int p, int q) { // 合并
35+
p = find(p);
36+
q = find(q);
37+
if (p == q) return;
4838
// 不按 rank,连接到字典序小的点
49-
if (rootP < rootQ) {
50-
fa[rootQ] = rootP;
51-
} else {
52-
fa[rootP] = rootQ;
53-
}
39+
if (p < q) fa[q] = p;
40+
else fa[p] = q;
5441
}
5542
}
5643
}

‎leetcode/leetcode-17/src/main/java/Solution1638.java

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,25 @@ public int countSubstrings(String s, String t) {
1717
}
1818
return ans;
1919
}
20+
21+
public int countSubstrings2(String S, String T) {
22+
char[] s = S.toCharArray();
23+
char[] t = T.toCharArray();
24+
int n = s.length;
25+
int m = t.length;
26+
int ans = 0;
27+
for (int d = 1 - m; d < n; ++d) { // d=i-j, j=i-d
28+
int i = Math.max(d, 0);
29+
for (int k0 = i - 1, k1 = k0; i < n && i - d < m; ++i) {
30+
if (s[i] != t[i - d]) {
31+
k0 = k1; // 上上一个不同
32+
k1 = i; // 上一个不同
33+
}
34+
ans += k1 - k0;
35+
}
36+
}
37+
return ans;
38+
}
2039
}
2140
/*
2241
1638. 统计只差一个字符的子串数目
@@ -32,4 +51,6 @@ public int countSubstrings(String s, String t) {
3251
3352
枚举。
3453
时间复杂度 O(mn * min(m,n))。
54+
【图解】非暴力 O(nm) 算法
55+
https://leetcode.cn/problems/count-substrings-that-differ-by-one-character/solutions/2192600/tu-jie-fei-bao-li-onm-suan-fa-pythonjava-k5og/
3556
*/

‎leetcode/leetcode-17/src/test/java/Solution1638Tests.java

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,7 @@ public void example1() {
1010
String t = "baba";
1111
int expected = 6;
1212
Assertions.assertEquals(expected, solution1638.countSubstrings(s, t));
13+
Assertions.assertEquals(expected, solution1638.countSubstrings2(s, t));
1314
}
1415

1516
@Test
@@ -18,6 +19,7 @@ public void example2() {
1819
String t = "bb";
1920
int expected = 3;
2021
Assertions.assertEquals(expected, solution1638.countSubstrings(s, t));
22+
Assertions.assertEquals(expected, solution1638.countSubstrings2(s, t));
2123
}
2224

2325
@Test
@@ -26,6 +28,7 @@ public void example3() {
2628
String t = "a";
2729
int expected = 0;
2830
Assertions.assertEquals(expected, solution1638.countSubstrings(s, t));
31+
Assertions.assertEquals(expected, solution1638.countSubstrings2(s, t));
2932
}
3033

3134
@Test
@@ -34,5 +37,6 @@ public void example4() {
3437
String t = "bbc";
3538
int expected = 10;
3639
Assertions.assertEquals(expected, solution1638.countSubstrings(s, t));
40+
Assertions.assertEquals(expected, solution1638.countSubstrings2(s, t));
3741
}
3842
}

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