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Commit 36818e7

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feat: update solutions to lc problem: No.0018,0454
- No.0018.4Sum - No.0454.4Sum II
1 parent bacc49b commit 36818e7

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5 files changed

+81
-80
lines changed

5 files changed

+81
-80
lines changed

‎solution/0000-0099/0018.4Sum/README.md‎

Lines changed: 26 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -46,7 +46,11 @@
4646

4747
<!-- 这里可写通用的实现逻辑 -->
4848

49-
"排序 + 双指针"实现。
49+
**方法一:排序 + 双指针**
50+
51+
该题和 [0015.三数之和](../0015.3Sum/README.md) 相似,解法也相似。
52+
53+
时间复杂度为 $O(n^3),ドル空间复杂度为 $O(\log n),ドル其中 $n$ 是数组的长度。
5054

5155
<!-- tabs:start -->
5256

@@ -171,40 +175,35 @@ public:
171175
172176
```go
173177
func fourSum(nums []int, target int) [][]int {
174-
n, res := len(nums), make([][]int, 0)
175-
if n < 4 {
176-
return res
177-
}
178+
ans, n := [][]int{}, len(nums)
178179
sort.Ints(nums)
179-
for i := 0; i < n-3; i++ {
180-
if i > 0 && nums[i] == nums[i-1] {
181-
continue
182-
}
183-
for j := i + 1; j < n-2; j++ {
184-
if j > i+1 && nums[j] == nums[j-1] {
185-
continue
186-
}
187-
k, l := j+1, n-1
188-
for k < l {
189-
if nums[i]+nums[j]+nums[k]+nums[l] == target {
190-
res = append(res, []int{nums[i], nums[j], nums[k], nums[l]})
191-
k++
192-
l--
193-
for k < n && nums[k] == nums[k-1] {
194-
k++
180+
for i := 0; i < n; i++ {
181+
for j := i + 1; j < n; j++ {
182+
for l, r := j+1, n-1; l < r; {
183+
if nums[i]+nums[j]+nums[l]+nums[r] == target {
184+
ans = append(ans, []int{nums[i], nums[j], nums[l], nums[r]})
185+
l, r = l+1, r-1
186+
for l < r && nums[l] == nums[l-1] {
187+
l++
195188
}
196-
for l > j && nums[l] == nums[l+1] {
197-
l--
189+
for l < r && nums[r] == nums[r+1] {
190+
r--
198191
}
199-
} else if nums[i]+nums[j]+nums[k]+nums[l] < target {
200-
k++
192+
} else if nums[i]+nums[j]+nums[l]+nums[r] < target {
193+
l++
201194
} else {
202-
l--
195+
r--
203196
}
204197
}
198+
for j+1 < n && nums[j+1] == nums[j] {
199+
j++
200+
}
201+
}
202+
for i+1 < n && nums[i+1] == nums[i] {
203+
i++
205204
}
206205
}
207-
return res
206+
return ans
208207
}
209208
```
210209

‎solution/0000-0099/0018.4Sum/README_EN.md‎

Lines changed: 25 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -40,6 +40,10 @@
4040

4141
## Solutions
4242

43+
**Approach 1: Two Pointers**
44+
45+
Time complexity $O(n^3),ドル Space complexity $O(\log n)$.
46+
4347
<!-- tabs:start -->
4448

4549
### **Python3**
@@ -159,40 +163,35 @@ public:
159163
160164
```go
161165
func fourSum(nums []int, target int) [][]int {
162-
n, res := len(nums), make([][]int, 0)
163-
if n < 4 {
164-
return res
165-
}
166+
ans, n := [][]int{}, len(nums)
166167
sort.Ints(nums)
167-
for i := 0; i < n-3; i++ {
168-
if i > 0 && nums[i] == nums[i-1] {
169-
continue
170-
}
171-
for j := i + 1; j < n-2; j++ {
172-
if j > i+1 && nums[j] == nums[j-1] {
173-
continue
174-
}
175-
k, l := j+1, n-1
176-
for k < l {
177-
if nums[i]+nums[j]+nums[k]+nums[l] == target {
178-
res = append(res, []int{nums[i], nums[j], nums[k], nums[l]})
179-
k++
180-
l--
181-
for k < n && nums[k] == nums[k-1] {
182-
k++
168+
for i := 0; i < n; i++ {
169+
for j := i + 1; j < n; j++ {
170+
for l, r := j+1, n-1; l < r; {
171+
if nums[i]+nums[j]+nums[l]+nums[r] == target {
172+
ans = append(ans, []int{nums[i], nums[j], nums[l], nums[r]})
173+
l, r = l+1, r-1
174+
for l < r && nums[l] == nums[l-1] {
175+
l++
183176
}
184-
for l > j && nums[l] == nums[l+1] {
185-
l--
177+
for l < r && nums[r] == nums[r+1] {
178+
r--
186179
}
187-
} else if nums[i]+nums[j]+nums[k]+nums[l] < target {
188-
k++
180+
} else if nums[i]+nums[j]+nums[l]+nums[r] < target {
181+
l++
189182
} else {
190-
l--
183+
r--
191184
}
192185
}
186+
for j+1 < n && nums[j+1] == nums[j] {
187+
j++
188+
}
189+
}
190+
for i+1 < n && nums[i+1] == nums[i] {
191+
i++
193192
}
194193
}
195-
return res
194+
return ans
196195
}
197196
```
198197

Lines changed: 22 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -1,36 +1,31 @@
11
func fourSum(nums []int, target int) [][]int {
2-
n, res := len(nums), make([][]int, 0)
3-
if n < 4 {
4-
return res
5-
}
2+
ans, n := [][]int{}, len(nums)
63
sort.Ints(nums)
7-
for i := 0; i < n-3; i++ {
8-
if i > 0 && nums[i] == nums[i-1] {
9-
continue
10-
}
11-
for j := i + 1; j < n-2; j++ {
12-
if j > i+1 && nums[j] == nums[j-1] {
13-
continue
14-
}
15-
k, l := j+1, n-1
16-
for k < l {
17-
if nums[i]+nums[j]+nums[k]+nums[l] == target {
18-
res = append(res, []int{nums[i], nums[j], nums[k], nums[l]})
19-
k++
20-
l--
21-
for k < n && nums[k] == nums[k-1] {
22-
k++
4+
for i := 0; i < n; i++ {
5+
for j := i + 1; j < n; j++ {
6+
for l, r := j+1, n-1; l < r; {
7+
if nums[i]+nums[j]+nums[l]+nums[r] == target {
8+
ans = append(ans, []int{nums[i], nums[j], nums[l], nums[r]})
9+
l, r = l+1, r-1
10+
for l < r && nums[l] == nums[l-1] {
11+
l++
2312
}
24-
for l >j && nums[l] == nums[l+1] {
25-
l--
13+
for l <r && nums[r] == nums[r+1] {
14+
r--
2615
}
27-
} else if nums[i]+nums[j]+nums[k]+nums[l] < target {
28-
k++
16+
} else if nums[i]+nums[j]+nums[l]+nums[r] < target {
17+
l++
2918
} else {
30-
l--
19+
r--
3120
}
3221
}
22+
for j+1 < n && nums[j+1] == nums[j] {
23+
j++
24+
}
25+
}
26+
for i+1 < n && nums[i+1] == nums[i] {
27+
i++
3328
}
3429
}
35-
return res
36-
}
30+
return ans
31+
}

‎solution/0400-0499/0454.4Sum II/README.md‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -50,6 +50,10 @@
5050

5151
<!-- 这里可写通用的实现逻辑 -->
5252

53+
**方法一:分组 + 哈希表**
54+
55+
时间复杂度为 $O(n^2),ドル空间复杂度为 $O(n^2),ドル其中 $n$ 是数组的长度。
56+
5357
<!-- tabs:start -->
5458

5559
### **Python3**

‎solution/0400-0499/0454.4Sum II/README_EN.md‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -44,6 +44,10 @@ The two tuples are:
4444

4545
## Solutions
4646

47+
**Approach 1: HashMap**
48+
49+
Time complexity $O(n^2),ドル Space complexity $O(n^2)$.
50+
4751
<!-- tabs:start -->
4852

4953
### **Python3**

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