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feat: add solutions to lc/lcof2 problems #1647

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Sep 19, 2023
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feat: add solutions to lc/lcof2 problems #1647

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150 changes: 101 additions & 49 deletions lcof2/剑指 Offer II 037. 小行星碰撞/README.md
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Expand Up @@ -58,12 +58,16 @@

<!-- 这里可写通用的实现逻辑 -->

可以类比成左右括号匹配：
**方法一：栈**

- 向右移动的小行星（左括号）：不会引发碰撞，直接入栈
- 向左移动的小行星（右括号）：可能会和之前向右移动的小行星发生碰撞，特殊处理
我们从左到右遍历每个小行星 $x$，由于每个小行星可能与之前的多个小行星发生碰撞，考虑用栈来存储。

因为答案需要碰撞后剩下的所有小行星，相当于栈里最后剩下的元素，所以可以直接用数组表示栈
- 对于当前小行星，如果 $x \gt 0$，那么它一定不会跟前面的小行星发生碰撞，我们可以直接将 $x$ 入栈。
- 否则，如果栈不为空并且栈顶元素大于 $0$，且栈顶元素小于 $-x$，那么栈顶元素对应的小行星会发生爆炸，我们循环将栈顶元素出栈，直到不满足条件。此时如果栈顶元素等于 $-x$，那么两个小行星会发生爆炸，只需要将栈顶元素出栈即可；如果栈为空，或者栈顶元素小于 $0$，那么当前小行星不会发生碰撞，我们将 $x$ 入栈。

最后我们返回栈中的元素即为答案。

时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 是数组 $asteroids$ 的长度。

<!-- tabs:start -->

Expand All @@ -74,18 +78,18 @@
```python
class Solution:
def asteroidCollision(self, asteroids: List[int]) -> List[int]:
ans = []
for a in asteroids:
if a > 0:
ans.append(a)
stk = []
for x in asteroids:
if x > 0:
stk.append(x)
else:
while len(ans) > 0 and ans[-1] > 0 and ans[-1] < -a:
ans.pop()
if len(ans) > 0 and ans[-1] == -a:
ans.pop()
elif len(ans) == 0 or ans[-1] < -a:
ans.append(a)
return ans
while stk and stk[-1] > 0 and stk[-1] < -x:
stk.pop()
if stk and stk[-1] == -x:
stk.pop()
elif not stk or stk[-1] < 0:
stk.append(x)
return stk
```

### **Java**
Expand All @@ -95,22 +99,22 @@ class Solution:
```java
class Solution {
public int[] asteroidCollision(int[] asteroids) {
Deque<Integer> d = new ArrayDeque<>();
for (int a : asteroids) {
if (a > 0) {
d.offerLast(a);
Deque<Integer> stk = new ArrayDeque<>();
for (int x : asteroids) {
if (x > 0) {
stk.offerLast(x);
} else {
while (!d.isEmpty() && d.peekLast() > 0 && d.peekLast() < -a) {
d.pollLast();
while (!stk.isEmpty() && stk.peekLast() > 0 && stk.peekLast() < -x) {
stk.pollLast();
}
if (!d.isEmpty() && d.peekLast() == -a) {
d.pollLast();
} else if (d.isEmpty() || d.peekLast() < -a) {
d.offerLast(a);
if (!stk.isEmpty() && stk.peekLast() == -x) {
stk.pollLast();
} else if (stk.isEmpty() || stk.peekLast() < 0) {
stk.offerLast(x);
}
}
}
return d.stream().mapToInt(Integer::valueOf).toArray();
return stk.stream().mapToInt(Integer::valueOf).toArray();
}
}
```
Expand All @@ -121,46 +125,94 @@ class Solution {
class Solution {
public:
vector<int> asteroidCollision(vector<int>& asteroids) {
vector<int> ans;
for (int a : asteroids) {
if (a > 0) {
ans.push_back(a);
vector<int> stk;
for (int x : asteroids) {
if (x > 0) {
stk.push_back(x);
} else {
while (!ans.empty() && ans.back() > 0 && ans.back() < -a) {
ans.pop_back();
while (stk.size() && stk.back() > 0 && stk.back() < -x) {
stk.pop_back();
}
if (!ans.empty() && ans.back() == -a) {
ans.pop_back();
} else if (ans.empty() || ans.back() < -a) {
ans.push_back(a);
if (stk.size() && stk.back() == -x) {
stk.pop_back();
} else if (stk.empty() || stk.back() < 0) {
stk.push_back(x);
}
}
}
return ans;
return stk;
}
};
```

### **Go**

```go
func asteroidCollision(asteroids []int) []int {
var ans []int
for _, a := range asteroids {
if a > 0 {
ans = append(ans, a)
func asteroidCollision(asteroids []int) (stk []int) {
for _, x := range asteroids {
if x > 0 {
stk = append(stk, x)
} else {
for len(ans) > 0 && ans[len(ans)-1] > 0 && ans[len(ans)-1] < -a {
ans = ans[:len(ans)-1]
for len(stk) > 0 && stk[len(stk)-1] > 0 && stk[len(stk)-1] < -x {
stk = stk[:len(stk)-1]
}
if len(ans) > 0 && ans[len(ans)-1] == -a {
ans = ans[:len(ans)-1]
} else if len(ans) == 0 || ans[len(ans)-1] < -a {
ans = append(ans, a)
if len(stk) > 0 && stk[len(stk)-1] == -x {
stk = stk[:len(stk)-1]
} else if len(stk) == 0 || stk[len(stk)-1] < 0 {
stk = append(stk, x)
}
}
}
return ans
return
}
```

### **TypeScript**

```ts
function asteroidCollision(asteroids: number[]): number[] {
const stk: number[] = [];
for (const x of asteroids) {
if (x > 0) {
stk.push(x);
} else {
while (stk.length && stk.at(-1) > 0 && stk.at(-1) < -x) {
stk.pop();
}
if (stk.length && stk.at(-1) === -x) {
stk.pop();
} else if (!stk.length || stk.at(-1) < 0) {
stk.push(x);
}
}
}
return stk;
}
```

### **Rust**

```rust
impl Solution {
#[allow(dead_code)]
pub fn asteroid_collision(asteroids: Vec<i32>) -> Vec<i32> {
let mut stk = Vec::new();
for &x in &asteroids {
if x > 0 {
stk.push(x);
} else {
while !stk.is_empty() && *stk.last().unwrap() > 0 && *stk.last().unwrap() < -x {
stk.pop();
}
if !stk.is_empty() && *stk.last().unwrap() == -x {
stk.pop();
} else if stk.is_empty() || *stk.last().unwrap() < 0 {
stk.push(x);
}
}
}
stk
}
}
```

Expand Down
42 changes: 21 additions & 21 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.cpp
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Original file line number Diff line number Diff line change
@@ -1,21 +1,21 @@
class Solution {
public:
vector<int> asteroidCollision(vector<int>& asteroids) {
vector<int> ans;
for (int a : asteroids) {
if (a > 0) {
ans.push_back(a);
} else {
while (!ans.empty() && ans.back() > 0 && ans.back() < -a) {
ans.pop_back();
}
if (!ans.empty() && ans.back() == -a) {
ans.pop_back();
} else if (ans.empty() || ans.back() < -a) {
ans.push_back(a);
}
}
}
return ans;
}
};
class Solution {
public:
vector<int> asteroidCollision(vector<int>& asteroids) {
vector<int> stk;
for (int x : asteroids) {
if (x > 0) {
stk.push_back(x);
} else {
while (stk.size() && stk.back() > 0 && stk.back() < -x) {
stk.pop_back();
}
if (stk.size() && stk.back() == -x) {
stk.pop_back();
} else if (stk.empty() || stk.back() < 0) {
stk.push_back(x);
}
}
}
return stk;
}
};
23 changes: 11 additions & 12 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.go
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Original file line number Diff line number Diff line change
@@ -1,18 +1,17 @@
func asteroidCollision(asteroids []int) []int {
var ans []int
for _, a := range asteroids {
if a > 0 {
ans = append(ans, a)
func asteroidCollision(asteroids []int) (stk []int) {
for _, x := range asteroids {
if x > 0 {
stk = append(stk, x)
} else {
for len(ans) > 0 && ans[len(ans)-1] > 0 && ans[len(ans)-1] < -a {
ans = ans[:len(ans)-1]
for len(stk) > 0 && stk[len(stk)-1] > 0 && stk[len(stk)-1] < -x {
stk = stk[:len(stk)-1]
}
if len(ans) > 0 && ans[len(ans)-1] == -a {
ans = ans[:len(ans)-1]
} else if len(ans) == 0 || ans[len(ans)-1] < -a {
ans = append(ans, a)
if len(stk) > 0 && stk[len(stk)-1] == -x {
stk = stk[:len(stk)-1]
} else if len(stk) == 0 || stk[len(stk)-1] < 0 {
stk = append(stk, x)
}
}
}
return ans
return
}
40 changes: 20 additions & 20 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.java
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Original file line number Diff line number Diff line change
@@ -1,20 +1,20 @@
class Solution {
public int[] asteroidCollision(int[] asteroids) {
Deque<Integer> d = new ArrayDeque<>();
for (int a : asteroids) {
if (a > 0) {
d.offerLast(a);
} else {
while (!d.isEmpty() && d.peekLast() > 0 && d.peekLast() < -a) {
d.pollLast();
}
if (!d.isEmpty() && d.peekLast() == -a) {
d.pollLast();
} else if (d.isEmpty() || d.peekLast() < -a) {
d.offerLast(a);
}
}
}
return d.stream().mapToInt(Integer::valueOf).toArray();
}
}
class Solution {
public int[] asteroidCollision(int[] asteroids) {
Deque<Integer> stk = new ArrayDeque<>();
for (int x : asteroids) {
if (x > 0) {
stk.offerLast(x);
} else {
while (!stk.isEmpty() && stk.peekLast() > 0 && stk.peekLast() < -x) {
stk.pollLast();
}
if (!stk.isEmpty() && stk.peekLast() == -x) {
stk.pollLast();
} else if (stk.isEmpty() || stk.peekLast() < 0) {
stk.offerLast(x);
}
}
}
return stk.stream().mapToInt(Integer::valueOf).toArray();
}
}
28 changes: 14 additions & 14 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.py
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
class Solution:
def asteroidCollision(self, asteroids: List[int]) -> List[int]:
ans = []
for a in asteroids:
if a > 0:
ans.append(a)
else:
while len(ans) > 0 and ans[-1] > 0 and ans[-1] < -a:
ans.pop()
if len(ans) > 0 and ans[-1] == -a:
ans.pop()
elif len(ans) == 0 or ans[-1] < -a:
ans.append(a)
return ans
class Solution:
def asteroidCollision(self, asteroids: List[int]) -> List[int]:
stk = []
for x in asteroids:
if x > 0:
stk.append(x)
else:
while stk and stk[-1] > 0 and stk[-1] < -x:
stk.pop()
if stk and stk[-1] == -x:
stk.pop()
elif not stk or stk[-1] < 0:
stk.append(x)
return stk
21 changes: 21 additions & 0 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
impl Solution {
#[allow(dead_code)]
pub fn asteroid_collision(asteroids: Vec<i32>) -> Vec<i32> {
let mut stk = Vec::new();
for &x in &asteroids {
if x > 0 {
stk.push(x);
} else {
while !stk.is_empty() && *stk.last().unwrap() > 0 && *stk.last().unwrap() < -x {
stk.pop();
}
if !stk.is_empty() && *stk.last().unwrap() == -x {
stk.pop();
} else if stk.is_empty() || *stk.last().unwrap() < 0 {
stk.push(x);
}
}
}
stk
}
}
18 changes: 18 additions & 0 deletions lcof2/剑指 Offer II 037. 小行星碰撞/Solution.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
function asteroidCollision(asteroids: number[]): number[] {
const stk: number[] = [];
for (const x of asteroids) {
if (x > 0) {
stk.push(x);
} else {
while (stk.length && stk.at(-1) > 0 && stk.at(-1) < -x) {
stk.pop();
}
if (stk.length && stk.at(-1) === -x) {
stk.pop();
} else if (!stk.length || stk.at(-1) < 0) {
stk.push(x);
}
}
}
return stk;
}
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