Skip to content

Commit 368c441

Browse files
yanglbmeyanglbme
authored
feat: add solutions to lc problems: No.1546,1547,1551 (doocs#2072)
* No.1546.Maximum Number of Non-Overlapping Subarrays With Sum Equals Target * No.1547.Minimum Cost to Cut a Stick * No.1551.Minimum Operations to Make Array Equal
1 parent 14db2a5 commit 368c441

File tree

9 files changed

+216
-131
lines changed

9 files changed

+216
-131
lines changed

‎solution/1500-1599/1546.Maximum Number of Non-Overlapping Subarrays With Sum Equals Target/README.md

+50-32
Original file line numberDiff line numberDiff line change
@@ -52,9 +52,11 @@
5252

5353
<!-- 这里可写通用的实现逻辑 -->
5454

55-
贪心 + 前缀和。ans 表示结果，初始值为 0。
55+
**方法一：贪心 + 前缀和 + 哈希表**
5656

57-
贪心：当我们发现以下标 i 结尾的子数组和为 target 时，ans++，然后继续往后查找。
57+
我们遍历数组 $nums$，利用前缀和 + 哈希表的方法，寻找和为 $target$ 的子数组，若找到，则答案加一，然后我们将前缀和置为 $0$，继续遍历数组 $nums$，直到遍历完整个数组。
58+
59+
时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为数组 $nums$ 的长度。
5860

5961
<!-- tabs:start -->
6062

@@ -65,18 +67,18 @@
6567
```python
6668
class Solution:
6769
def maxNonOverlapping(self, nums: List[int], target: int) -> int:
68-
i, n = 0, len(nums)
6970
ans = 0
71+
i, n = 0, len(nums)
7072
while i < n:
7173
s = 0
72-
seen = {0}
74+
vis = {0}
7375
while i < n:
7476
s += nums[i]
75-
if s - target in seen:
77+
if s - target in vis:
7678
ans += 1
7779
break
7880
i += 1
79-
seen.add(s)
81+
vis.add(s)
8082
i += 1
8183
return ans
8284
```
@@ -88,22 +90,20 @@ class Solution:
8890
```java
8991
class Solution {
9092
public int maxNonOverlapping(int[] nums, int target) {
91-
int i = 0, n = nums.length;
92-
int ans = 0;
93-
while (i < n) {
93+
int ans = 0, n = nums.length;
94+
for (int i = 0; i < n; ++i) {
95+
Set<Integer> vis = new HashSet<>();
9496
int s = 0;
95-
Set<Integer> seen = new HashSet<>();
96-
seen.add(0);
97+
vis.add(0);
9798
while (i < n) {
9899
s += nums[i];
99-
if (seen.contains(s - target)) {
100+
if (vis.contains(s - target)) {
100101
++ans;
101102
break;
102103
}
103104
++i;
104-
seen.add(s);
105+
vis.add(s);
105106
}
106-
++i;
107107
}
108108
return ans;
109109
}
@@ -116,22 +116,19 @@ class Solution {
116116
class Solution {
117117
public:
118118
int maxNonOverlapping(vector<int>& nums, int target) {
119-
int i = 0, n = nums.size();
120-
int ans = 0;
121-
while (i < n) {
119+
int ans = 0, n = nums.size();
120+
for (int i = 0; i < n; ++i) {
121+
unordered_set<int> vis{{0}};
122122
int s = 0;
123-
unordered_set<int> seen;
124-
seen.insert(0);
125123
while (i < n) {
126124
s += nums[i];
127-
if (seen.count(s - target)) {
125+
if (vis.count(s - target)) {
128126
++ans;
129127
break;
130128
}
131129
++i;
132-
seen.insert(s);
130+
vis.insert(s);
133131
}
134-
++i;
135132
}
136133
return ans;
137134
}
@@ -141,23 +138,44 @@ public:
141138
### **Go**
142139
143140
```go
144-
func maxNonOverlapping(nums []int, target int) int {
145-
i, n, ans := 0, len(nums), 0
146-
for i < n {
141+
func maxNonOverlapping(nums []int, target int) (ans int) {
142+
n := len(nums)
143+
for i := 0; i < n; i++ {
147144
s := 0
148-
seen := map[int]bool{0: true}
149-
for i < n {
145+
vis := map[int]bool{0: true}
146+
for ; i < n; i++ {
150147
s += nums[i]
151-
if seen[s-target] {
148+
if vis[s-target] {
152149
ans++
153150
break
154151
}
155-
seen[s] = true
156-
i++
152+
vis[s] = true
157153
}
158-
i++
159154
}
160-
return ans
155+
return
156+
}
157+
```
158+
159+
### **TypeScript**
160+
161+
```ts
162+
function maxNonOverlapping(nums: number[], target: number): number {
163+
const n = nums.length;
164+
let ans = 0;
165+
for (let i = 0; i < n; ++i) {
166+
let s = 0;
167+
const vis: Set<number> = new Set();
168+
vis.add(0);
169+
for (; i < n; ++i) {
170+
s += nums[i];
171+
if (vis.has(s - target)) {
172+
++ans;
173+
break;
174+
}
175+
vis.add(s);
176+
}
177+
}
178+
return ans;
161179
}
162180
```
163181

‎solution/1500-1599/1546.Maximum Number of Non-Overlapping Subarrays With Sum Equals Target/README_EN.md

+52-30
Original file line numberDiff line numberDiff line change
@@ -35,25 +35,31 @@
3535

3636
## Solutions
3737

38+
**Solution 1: Greedy + Prefix Sum + Hash Table**
39+
40+
We traverse the array $nums$, using the method of prefix sum + hash table, to find subarrays with a sum of $target$. If found, we increment the answer by one, then we set the prefix sum to $0$ and continue to traverse the array $nums$ until the entire array is traversed.
41+
42+
The time complexity is $O(n)$, and the space complexity is $O(n)$. Here, $n$ is the length of the array $nums$.
43+
3844
<!-- tabs:start -->
3945

4046
### **Python3**
4147

4248
```python
4349
class Solution:
4450
def maxNonOverlapping(self, nums: List[int], target: int) -> int:
45-
i, n = 0, len(nums)
4651
ans = 0
52+
i, n = 0, len(nums)
4753
while i < n:
4854
s = 0
49-
seen = {0}
55+
vis = {0}
5056
while i < n:
5157
s += nums[i]
52-
if s - target in seen:
58+
if s - target in vis:
5359
ans += 1
5460
break
5561
i += 1
56-
seen.add(s)
62+
vis.add(s)
5763
i += 1
5864
return ans
5965
```
@@ -63,22 +69,20 @@ class Solution:
6369
```java
6470
class Solution {
6571
public int maxNonOverlapping(int[] nums, int target) {
66-
int i = 0, n = nums.length;
67-
int ans = 0;
68-
while (i < n) {
72+
int ans = 0, n = nums.length;
73+
for (int i = 0; i < n; ++i) {
74+
Set<Integer> vis = new HashSet<>();
6975
int s = 0;
70-
Set<Integer> seen = new HashSet<>();
71-
seen.add(0);
76+
vis.add(0);
7277
while (i < n) {
7378
s += nums[i];
74-
if (seen.contains(s - target)) {
79+
if (vis.contains(s - target)) {
7580
++ans;
7681
break;
7782
}
7883
++i;
79-
seen.add(s);
84+
vis.add(s);
8085
}
81-
++i;
8286
}
8387
return ans;
8488
}
@@ -91,22 +95,19 @@ class Solution {
9195
class Solution {
9296
public:
9397
int maxNonOverlapping(vector<int>& nums, int target) {
94-
int i = 0, n = nums.size();
95-
int ans = 0;
96-
while (i < n) {
98+
int ans = 0, n = nums.size();
99+
for (int i = 0; i < n; ++i) {
100+
unordered_set<int> vis{{0}};
97101
int s = 0;
98-
unordered_set<int> seen;
99-
seen.insert(0);
100102
while (i < n) {
101103
s += nums[i];
102-
if (seen.count(s - target)) {
104+
if (vis.count(s - target)) {
103105
++ans;
104106
break;
105107
}
106108
++i;
107-
seen.insert(s);
109+
vis.insert(s);
108110
}
109-
++i;
110111
}
111112
return ans;
112113
}
@@ -116,23 +117,44 @@ public:
116117
### **Go**
117118
118119
```go
119-
func maxNonOverlapping(nums []int, target int) int {
120-
i, n, ans := 0, len(nums), 0
121-
for i < n {
120+
func maxNonOverlapping(nums []int, target int) (ans int) {
121+
n := len(nums)
122+
for i := 0; i < n; i++ {
122123
s := 0
123-
seen := map[int]bool{0: true}
124-
for i < n {
124+
vis := map[int]bool{0: true}
125+
for ; i < n; i++ {
125126
s += nums[i]
126-
if seen[s-target] {
127+
if vis[s-target] {
127128
ans++
128129
break
129130
}
130-
seen[s] = true
131-
i++
131+
vis[s] = true
132132
}
133-
i++
134133
}
135-
return ans
134+
return
135+
}
136+
```
137+
138+
### **TypeScript**
139+
140+
```ts
141+
function maxNonOverlapping(nums: number[], target: number): number {
142+
const n = nums.length;
143+
let ans = 0;
144+
for (let i = 0; i < n; ++i) {
145+
let s = 0;
146+
const vis: Set<number> = new Set();
147+
vis.add(0);
148+
for (; i < n; ++i) {
149+
s += nums[i];
150+
if (vis.has(s - target)) {
151+
++ans;
152+
break;
153+
}
154+
vis.add(s);
155+
}
156+
}
157+
return ans;
136158
}
137159
```
138160

‎solution/1500-1599/1546.Maximum Number of Non-Overlapping Subarrays With Sum Equals Target/Solution.cpp

+19-22
Original file line numberDiff line numberDiff line change
@@ -1,23 +1,20 @@
1-
class Solution {
2-
public:
3-
int maxNonOverlapping(vector<int>& nums, int target) {
4-
int i = 0, n = nums.size();
5-
int ans = 0;
6-
while (i < n) {
7-
int s = 0;
8-
unordered_set<int> seen;
9-
seen.insert(0);
10-
while (i < n) {
11-
s += nums[i];
12-
if (seen.count(s - target)) {
13-
++ans;
14-
break;
15-
}
16-
++i;
17-
seen.insert(s);
18-
}
19-
++i;
20-
}
21-
return ans;
22-
}
1+
class Solution {
2+
public:
3+
int maxNonOverlapping(vector<int>& nums, int target) {
4+
int ans = 0, n = nums.size();
5+
for (int i = 0; i < n; ++i) {
6+
unordered_set<int> vis{{0}};
7+
int s = 0;
8+
while (i < n) {
9+
s += nums[i];
10+
if (vis.count(s - target)) {
11+
++ans;
12+
break;
13+
}
14+
++i;
15+
vis.insert(s);
16+
}
17+
}
18+
return ans;
19+
}
2320
};

‎solution/1500-1599/1546.Maximum Number of Non-Overlapping Subarrays With Sum Equals Target/Solution.go

+8-10
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,16 @@
1-
func maxNonOverlapping(nums []int, target int) int {
2-
i, n, ans := 0, len(nums), 0
3-
for i < n {
1+
func maxNonOverlapping(nums []int, target int) (ans int) {
2+
n := len(nums)
3+
for i := 0; i < n; i++ {
44
s := 0
5-
seen := map[int]bool{0: true}
6-
for i < n {
5+
vis := map[int]bool{0: true}
6+
for ; i < n; i++ {
77
s += nums[i]
8-
if seen[s-target] {
8+
if vis[s-target] {
99
ans++
1010
break
1111
}
12-
seen[s] = true
13-
i++
12+
vis[s] = true
1413
}
15-
i++
1614
}
17-
return ans
15+
return
1816
}

0 commit comments

Comments
 (0)