算法设计与应用基础：第二周（1）

241. Different Ways to Add Parentheses

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• Difficulty: Medium
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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".

((2-1)-1) = 0
(2-(1-1)) = 2

Output: [0, 2]

Example 2

Input: "2*3-4*5"

(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

Output: [-34, -14, -10, -10, 10]




题解：

考虑分治，遍历整个字符串，若遍历到符号，则将其两边的子字符串递归，算出两边的值之后再通过判断符号来做最后一步的计算，实际上即为越先遍历到的符号越后算。

代码如下：