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Commit 1fc0cbd

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feat: add solutions to lc problem: No.2272
No.2272.Substring With Largest Variance
1 parent 624501e commit 1fc0cbd

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11 files changed

+343
-38
lines changed

11 files changed

+343
-38
lines changed

‎solution/0900-0999/0934.Shortest Bridge/README.md‎

Lines changed: 9 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -78,21 +78,21 @@ class Solution:
7878
def dfs(i, j):
7979
q.append((i, j))
8080
grid[i][j] = 2
81-
for a, b in dirs:
81+
for a, b in pairwise(dirs):
8282
x, y = i + a, j + b
8383
if 0 <= x < n and 0 <= y < n and grid[x][y] == 1:
8484
dfs(x, y)
8585

8686
n = len(grid)
87-
dirs = ((0, 1), (0, -1), (1, 0), (-1, 0))
87+
dirs = (-1, 0, 1, 0, -1)
8888
q = deque()
8989
i, j = next((i, j) for i in range(n) for j in range(n) if grid[i][j])
9090
dfs(i, j)
9191
ans = 0
9292
while 1:
9393
for _ in range(len(q)):
9494
i, j = q.popleft()
95-
for a, b in dirs:
95+
for a, b in pairwise(dirs):
9696
x, y = i + a, j + b
9797
if 0 <= x < n and 0 <= y < n:
9898
if grid[x][y] == 1:
@@ -163,15 +163,13 @@ class Solution {
163163
### **C++**
164164

165165
```cpp
166-
using pii = pair<int, int>;
167-
168166
class Solution {
169167
public:
170168
const static inline vector<int> dirs = {-1, 0, 1, 0, -1};
171169

172170
int shortestBridge(vector<vector<int>>& grid) {
173171
int n = grid.size();
174-
queue<pii> q;
172+
queue<pair<int, int>> q;
175173
function<void(int, int)> dfs = [&](int i, int j) {
176174
grid[i][j] = 2;
177175
q.emplace(i, j);
@@ -193,11 +191,11 @@ public:
193191
}
194192
int ans = 0;
195193
while (1) {
196-
for (int k = q.size(); k; --k) {
194+
for (int h = q.size(); h; --h) {
197195
auto [i, j] = q.front();
198196
q.pop();
199-
for (int h = 0; h < 4; ++h) {
200-
int x = i + dirs[h], y = j + dirs[h + 1];
197+
for (int k = 0; k < 4; ++k) {
198+
int x = i + dirs[k], y = j + dirs[k + 1];
201199
if (x >= 0 && x < n && y >= 0 && y < n) {
202200
if (grid[x][y] == 1) return ans;
203201
if (grid[x][y] == 0) {
@@ -216,7 +214,7 @@ public:
216214
### **Go**
217215

218216
```go
219-
func shortestBridge(grid [][]int) int {
217+
func shortestBridge(grid [][]int) (ansint) {
220218
n := len(grid)
221219
dirs := []int{-1, 0, 1, 0, -1}
222220
type pair struct{ i, j int }
@@ -241,7 +239,6 @@ func shortestBridge(grid [][]int) int {
241239
}
242240
}
243241
}
244-
ans := 0
245242
for {
246243
for i := len(q); i > 0; i-- {
247244
p := q[0]
@@ -250,7 +247,7 @@ func shortestBridge(grid [][]int) int {
250247
x, y := p.i+dirs[k], p.j+dirs[k+1]
251248
if x >= 0 && x < n && y >= 0 && y < n {
252249
if grid[x][y] == 1 {
253-
return ans
250+
return
254251
}
255252
if grid[x][y] == 0 {
256253
grid[x][y] = 2

‎solution/0900-0999/0934.Shortest Bridge/README_EN.md‎

Lines changed: 9 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -58,21 +58,21 @@ class Solution:
5858
def dfs(i, j):
5959
q.append((i, j))
6060
grid[i][j] = 2
61-
for a, b in dirs:
61+
for a, b in pairwise(dirs):
6262
x, y = i + a, j + b
6363
if 0 <= x < n and 0 <= y < n and grid[x][y] == 1:
6464
dfs(x, y)
6565

6666
n = len(grid)
67-
dirs = ((0, 1), (0, -1), (1, 0), (-1, 0))
67+
dirs = (-1, 0, 1, 0, -1)
6868
q = deque()
6969
i, j = next((i, j) for i in range(n) for j in range(n) if grid[i][j])
7070
dfs(i, j)
7171
ans = 0
7272
while 1:
7373
for _ in range(len(q)):
7474
i, j = q.popleft()
75-
for a, b in dirs:
75+
for a, b in pairwise(dirs):
7676
x, y = i + a, j + b
7777
if 0 <= x < n and 0 <= y < n:
7878
if grid[x][y] == 1:
@@ -141,15 +141,13 @@ class Solution {
141141
### **C++**
142142

143143
```cpp
144-
using pii = pair<int, int>;
145-
146144
class Solution {
147145
public:
148146
const static inline vector<int> dirs = {-1, 0, 1, 0, -1};
149147

150148
int shortestBridge(vector<vector<int>>& grid) {
151149
int n = grid.size();
152-
queue<pii> q;
150+
queue<pair<int, int>> q;
153151
function<void(int, int)> dfs = [&](int i, int j) {
154152
grid[i][j] = 2;
155153
q.emplace(i, j);
@@ -171,11 +169,11 @@ public:
171169
}
172170
int ans = 0;
173171
while (1) {
174-
for (int k = q.size(); k; --k) {
172+
for (int h = q.size(); h; --h) {
175173
auto [i, j] = q.front();
176174
q.pop();
177-
for (int h = 0; h < 4; ++h) {
178-
int x = i + dirs[h], y = j + dirs[h + 1];
175+
for (int k = 0; k < 4; ++k) {
176+
int x = i + dirs[k], y = j + dirs[k + 1];
179177
if (x >= 0 && x < n && y >= 0 && y < n) {
180178
if (grid[x][y] == 1) return ans;
181179
if (grid[x][y] == 0) {
@@ -194,7 +192,7 @@ public:
194192
### **Go**
195193

196194
```go
197-
func shortestBridge(grid [][]int) int {
195+
func shortestBridge(grid [][]int) (ansint) {
198196
n := len(grid)
199197
dirs := []int{-1, 0, 1, 0, -1}
200198
type pair struct{ i, j int }
@@ -219,7 +217,6 @@ func shortestBridge(grid [][]int) int {
219217
}
220218
}
221219
}
222-
ans := 0
223220
for {
224221
for i := len(q); i > 0; i-- {
225222
p := q[0]
@@ -228,7 +225,7 @@ func shortestBridge(grid [][]int) int {
228225
x, y := p.i+dirs[k], p.j+dirs[k+1]
229226
if x >= 0 && x < n && y >= 0 && y < n {
230227
if grid[x][y] == 1 {
231-
return ans
228+
return
232229
}
233230
if grid[x][y] == 0 {
234231
grid[x][y] = 2

‎solution/0900-0999/0934.Shortest Bridge/Solution.cpp‎

Lines changed: 4 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,10 @@
1-
using pii = pair<int, int>;
2-
31
class Solution {
42
public:
53
const static inline vector<int> dirs = {-1, 0, 1, 0, -1};
64

75
int shortestBridge(vector<vector<int>>& grid) {
86
int n = grid.size();
9-
queue<pii> q;
7+
queue<pair<int, int>> q;
108
function<void(int, int)> dfs = [&](int i, int j) {
119
grid[i][j] = 2;
1210
q.emplace(i, j);
@@ -28,11 +26,11 @@ class Solution {
2826
}
2927
int ans = 0;
3028
while (1) {
31-
for (int k = q.size(); k; --k) {
29+
for (int h = q.size(); h; --h) {
3230
auto [i, j] = q.front();
3331
q.pop();
34-
for (int h = 0; h < 4; ++h) {
35-
int x = i + dirs[h], y = j + dirs[h + 1];
32+
for (int k = 0; k < 4; ++k) {
33+
int x = i + dirs[k], y = j + dirs[k + 1];
3634
if (x >= 0 && x < n && y >= 0 && y < n) {
3735
if (grid[x][y] == 1) return ans;
3836
if (grid[x][y] == 0) {

‎solution/0900-0999/0934.Shortest Bridge/Solution.go‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
func shortestBridge(grid [][]int) int {
1+
func shortestBridge(grid [][]int) (ansint) {
22
n := len(grid)
33
dirs := []int{-1, 0, 1, 0, -1}
44
type pair struct{ i, j int }
@@ -23,7 +23,6 @@ func shortestBridge(grid [][]int) int {
2323
}
2424
}
2525
}
26-
ans := 0
2726
for {
2827
for i := len(q); i > 0; i-- {
2928
p := q[0]
@@ -32,7 +31,7 @@ func shortestBridge(grid [][]int) int {
3231
x, y := p.i+dirs[k], p.j+dirs[k+1]
3332
if x >= 0 && x < n && y >= 0 && y < n {
3433
if grid[x][y] == 1 {
35-
returnans
34+
return
3635
}
3736
if grid[x][y] == 0 {
3837
grid[x][y] = 2

‎solution/0900-0999/0934.Shortest Bridge/Solution.py‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -3,21 +3,21 @@ def shortestBridge(self, grid: List[List[int]]) -> int:
33
def dfs(i, j):
44
q.append((i, j))
55
grid[i][j] = 2
6-
for a, b in dirs:
6+
for a, b in pairwise(dirs):
77
x, y = i + a, j + b
88
if 0 <= x < n and 0 <= y < n and grid[x][y] == 1:
99
dfs(x, y)
1010

1111
n = len(grid)
12-
dirs = ((0, 1), (0, -1), (1, 0), (-1, 0))
12+
dirs = (-1, 0, 1, 0, -1)
1313
q = deque()
1414
i, j = next((i, j) for i in range(n) for j in range(n) if grid[i][j])
1515
dfs(i, j)
1616
ans = 0
1717
while 1:
1818
for _ in range(len(q)):
1919
i, j = q.popleft()
20-
for a, b in dirs:
20+
for a, b in pairwise(dirs):
2121
x, y = i + a, j + b
2222
if 0 <= x < n and 0 <= y < n:
2323
if grid[x][y] == 1:

‎solution/2200-2299/2272.Substring With Largest Variance/README.md‎

Lines changed: 119 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -50,22 +50,140 @@ s 中没有字母出现超过 1 次,所以 s 中每个子字符串的波动值
5050

5151
<!-- 这里可写通用的实现逻辑 -->
5252

53+
**方法一:枚举 + 动态规划**
54+
55+
由于字符集只包含小写字母,我们可以考虑枚举出现次数最多的字符 $a$ 以及出现次数最少的字符 $b$。对于一个子串来说,这两种字符出现的次数之差就是子串的波动值。
56+
57+
具体实现上,我们使用双重循环枚举 $a$ 和 $b,ドル用 $f[0]$ 记录以当前字符结尾的连续出现字符 $a$ 的个数,用 $f[1]$ 记录以当前字符结尾的,并且包含 $a$ 和 $b$ 的子串的波动值。迭代取 $f[1]$ 的最大值即可。
58+
59+
递推公式如下:
60+
61+
1. 如果当前字符为 $a,ドル则 $f[0]$ 和 $f[1]$ 都加 1ドル$;
62+
1. 如果当前字符为 $b,ドル则 $f[1]=\max(f[1]-1, f[0]-1),ドル而 $f[0]=0$;
63+
1. 否则,无需考虑。
64+
65+
注意,初始时将 $f[1]$ 赋值为一个负数最大值,可以保证更新答案时是合法的。
66+
67+
时间复杂度 $O(n\times C^2),ドル其中 $n$ 表示字符串 $s$ 的长度,而 $C$ 为字符集大小,本题中 $C=26$。
68+
5369
<!-- tabs:start -->
5470

5571
### **Python3**
5672

5773
<!-- 这里可写当前语言的特殊实现逻辑 -->
5874

5975
```python
60-
76+
class Solution:
77+
def largestVariance(self, s: str) -> int:
78+
ans = 0
79+
for a, b in permutations(ascii_lowercase, 2):
80+
if a == b:
81+
continue
82+
f = [0, -inf]
83+
for c in s:
84+
if c == a:
85+
f[0], f[1] = f[0] + 1, f[1] + 1
86+
elif c == b:
87+
f[1] = max(f[1] - 1, f[0] - 1)
88+
f[0] = 0
89+
if ans < f[1]:
90+
ans = f[1]
91+
return ans
6192
```
6293

6394
### **Java**
6495

6596
<!-- 这里可写当前语言的特殊实现逻辑 -->
6697

6798
```java
99+
class Solution {
100+
public int largestVariance(String s) {
101+
int n = s.length();
102+
int ans = 0;
103+
for (char a = 'a'; a <= 'z'; ++a) {
104+
for (char b = 'a'; b <= 'z'; ++b) {
105+
if (a == b) {
106+
continue;
107+
}
108+
int[] f = new int[] {0, -n};
109+
for (int i = 0; i < n; ++i) {
110+
if (s.charAt(i) == a) {
111+
f[0]++;
112+
f[1]++;
113+
} else if (s.charAt(i) == b) {
114+
f[1] = Math.max(f[0] - 1, f[1] - 1);
115+
f[0] = 0;
116+
}
117+
ans = Math.max(ans, f[1]);
118+
}
119+
}
120+
}
121+
return ans;
122+
}
123+
}
124+
```
125+
126+
### **C++**
127+
128+
```cpp
129+
class Solution {
130+
public:
131+
int largestVariance(string s) {
132+
int n = s.size();
133+
int ans = 0;
134+
for (char a = 'a'; a <= 'z'; ++a) {
135+
for (char b = 'a'; b <= 'z'; ++b) {
136+
if (a == b) continue;
137+
int f[2] = {0, -n};
138+
for (char c : s) {
139+
if (c == a) {
140+
f[0]++;
141+
f[1]++;
142+
} else if (c == b) {
143+
f[1] = max(f[1] - 1, f[0] - 1);
144+
f[0] = 0;
145+
}
146+
ans = max(ans, f[1]);
147+
}
148+
}
149+
}
150+
return ans;
151+
}
152+
};
153+
```
68154
155+
### **Go**
156+
157+
```go
158+
func largestVariance(s string) int {
159+
ans, n := 0, len(s)
160+
for a := 'a'; a <= 'z'; a++ {
161+
for b := 'a'; b <= 'z'; b++ {
162+
if a == b {
163+
continue
164+
}
165+
f := [2]int{0, -n}
166+
for _, c := range s {
167+
if c == a {
168+
f[0]++
169+
f[1]++
170+
} else if c == b {
171+
f[1] = max(f[1]-1, f[0]-1)
172+
f[0] = 0
173+
}
174+
ans = max(ans, f[1])
175+
}
176+
}
177+
}
178+
return ans
179+
}
180+
181+
func max(a, b int) int {
182+
if a > b {
183+
return a
184+
}
185+
return b
186+
}
69187
```
70188

71189
### **TypeScript**

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