[LeetCode 241] Different Ways to Add Parentheses

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]

solution:

Recursive to calculate left value and right value, then make combination.

public List<Integer> diffWaysToCompute(String input) {List<Integer> res = new ArrayList<>();for(int i=0;i<input.length();i++){char c = input.charAt(i);if('+' == c || '-' == c || '*' == c) {String lv = input.substring(0, i);String rv = input.substring(i+1);List<Integer> lefts = diffWaysToCompute(lv);List<Integer> rights = diffWaysToCompute(rv);for(int j : lefts) {for(int k: rights){int temp = 0;switch(c){case'+':temp = j+k;break;case'-':temp = j-k;break;case'*': temp = j*k;}res.add(temp);}}}}if(res.isEmpty()){res.add(Integer.valueOf(input));}return res;}

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