23.07.20 Today’s Leetcode

735. Asteroid Collision (medium)

My own solution, Dirty!!!

class Solution:
    def asteroidCollision(self, asteroids: List[int]) -> List[int]:

        def help(arr):
            res = []
            i = 0
            n = len(arr)
            while i < n - 1:
                a, b = arr[i], arr[i + 1]
                if a > 0 and b < 0:
                    if abs(a) < abs(b):
                        res.append(b)
                    if abs(a) > abs(b):
                        res.append(a)
                    i += 1
                else:
                    res.append(a)
                i += 1
            if i == n - 1:
                res.append(arr[-1])
            return res
        
        res = asteroids[:]
        prev = len(res)
        for i in range(prev):
            res = help(res)
            temp = min(len(res), prev)
            if prev == temp:
                break
            prev = temp
        
        return res

with Stack

class Solution:
    def asteroidCollision(self, asteroids: List[int]) -> List[int]:
        stack = []
        for a in asteroids:
            while stack and a < 0 and stack[-1] > 0:
                diff = a + stack[-1]
                if diff < 0:
                    stack.pop()
                elif diff > 0:
                    a = 0
                else:
                    a = 0
                    stack.pop() 
                   
            if a:
                stack.append(a)
                
        return stack