735. Asteroid Collision

[fockspaces]

老題目，但還沒掌握精髓

1. stack 來做連續比較
2. 當 stack top 為正，才需處理接下來發生的事
3. 列出條件，一個個處理

class Solution:
    def asteroidCollision(self, asteroids: List[int]) -> List[int]:
        stack = []
        for asteroid in asteroids:
            explode = False
            while stack and stack[-1] > 0:
                result = asteroid + stack[-1]
                if result > 0:
                    explode = True if asteroid < 0 else False
                    break
                elif result == 0:
                    stack.pop()
                    explode = True
                    break
                else:
                    stack.pop()
            if not explode:
                stack.append(asteroid)

        return stack

# 1. cur > ast: pass
# 2. cur == ast: pop and pass
# 3. cur < ast: pop     

[fockspaces]

GPT improve:

1. 用 while...else 來簡化判斷（避免掉 flag）
2. 巧妙用 continue 和 break 來分化 while 邏輯

class Solution:
    def asteroidCollision(self, asteroids: List[int]) -> List[int]:
        stack = []
        for asteroid in asteroids:
            # only collid with [+, -] case 
            while stack and asteroid < 0 < stack[-1]:
                if abs(stack[-1]) < abs(asteroid):
                    stack.pop()
                    continue
                elif abs(stack[-1]) == abs(asteroid):
                    stack.pop()
                break
            else:
                stack.append(asteroid)

        return stack

[fockspaces]

continue: 用於繼續執行判斷 break: 用於結束判斷

這邊 break 之所以分開，是因為 break handle 了全部 if 判斷中，沒用 continue 的欄位 如果要寫進去，則需要每個 elif 都 break 一次