0241._Different_Ways_to_Add_Parentheses.md

241. Different Ways to Add Parentheses

难度: Medium

刷题内容

原题连接

• https://leetcode.com/problems/different-ways-to-add-parentheses

内容描述

Given a string of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. The valid operators are +, - and *.

Example 1:

Input: "2-1-1"
Output: [0, 2]
Explanation: 
((2-1)-1) = 0 
(2-(1-1)) = 2
Example 2:

Input: "2*3-4*5"
Output: [-34, -14, -10, -10, 10]
Explanation: 
(2*(3-(4*5))) = -34 
((2*3)-(4*5)) = -14 
((2*(3-4))*5) = -10 
(2*((3-4)*5)) = -10 
(((2*3)-4)*5) = 10

解题方案

思路 1 - 时间复杂度: O(N)- 空间复杂度: O(N)******

递归

beats 84.41%

class Solution:
    def diffWaysToCompute(self, input):
        """
        :type input: str
        :rtype: List[int]
        """
        if input.isdigit():
            return [int(input)]
        res = []
        for i in range(len(input)):
            if input[i] in "-+*":
                res1 = self.diffWaysToCompute(input[:i])
                res2 = self.diffWaysToCompute(input[i+1:])
                res.extend(self.helper(j, k, input[i]) for j in res1 for k in res2)
        return res
    
    def helper(self, m, n, op):
        if op == "+":
            return m + n
        elif op == "-":
            return m - n
        else:
            return m * n