[leetcode][Medium][Stack] 150. Evaluate Reverse Polish Notation 풀이, 해설 (python)

https://leetcode.com/problems/evaluate-reverse-polish-notation/

Evaluate Reverse Polish Notation - LeetCode

 

1차 풀이

class Solution(object):
    def evalRPN(self, tokens):
        """
        :type tokens: List[str]
        :rtype: int
        """
        
        stack = [] 
        for t in tokens:
            if t not in ['/', '+', '-', '*']:
                stack.append(t)
            else : 
                n1 = int(stack.pop())
                n2 = int(stack.pop())
                
                if t == '/':
                    check = math.trunc(float(n2) / float(n1))
                    stack.append(check)
                elif t == '+':
                    stack.append(n2+n1)
                elif t == '-':
                    stack.append(n2-n1)
                elif t == '*':
                    stack.append(n2*n1)
            # print(stack)
        
        return int(stack.pop())

 

 

해설

https://www.youtube.com/watch?v=iu0082c4HDE

 

 

stack = [] 
for c in tokens:
    if c == '+':
        stack.append(stack.pop() + stack.pop())
    elif c == '-':
        a, b = stack.pop(), stack.pop()
        stack.append(b - a)
    elif c == '*':
        stack.append(stack.pop() * stack.pop())
    elif c == '/':
        a, b = stack.pop(), stack.pop()
        stack.append(int(float(b) / a))
    else:
        stack.append(int(c))

return stack[0]

 

나와 다르게 푼 풀이는 나눗셈인데 

나는 check = math.trunc(float(n2) / float(n1)) 이렇게 해서 풀었는데, 

해설에서는 stack.append(int(float(b) / a))로 쉽게 풀었다.