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  • (medium)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]

    Credits:
    Special thanks to @mithmatt for adding this problem and creating all test cases.

    解法思想:递归

    代码如下:

    public class Solution {
        public List<Integer> diffWaysToCompute(String input) {
            List<Integer> ret=new LinkedList<Integer>();
            int len=input.length();
            for(int i=0;i<len;i++){
                if(input.charAt(i)=='-'||
                   input.charAt(i)=='*'||
                   input.charAt(i)=='+'){
                       String part1=input.substring(0,i);
                       String part2=input.substring(i+1);
                       List<Integer> part1Ret=diffWaysToCompute(part1);
                       List<Integer> part2Ret=diffWaysToCompute(part2);
                       for(Integer p1:part1Ret){
                           for(Integer p2:part2Ret){
                               int c=0;
                               switch(input.charAt(i)){
                                   case '+':c=p1+p2;
                                       break;
                                   case '-':c=p1-p2;
                                       break;
                                   case '*': c=p1*p2;       
                               }
                               ret.add(c);
                           }
                       }
                   }
            }
            if(ret.size()==0){
                ret.add(Integer.valueOf(input));
            }
            return ret;
        }
    }
    

      运行结果:

          

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  • 原文地址:https://www.cnblogs.com/mlz-2019/p/4699756.html
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