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 *.
Input: "2-1-1".
((2-1)-1) = 0 (2-(1-1)) = 2
Output: [0, 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.
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java code:
public class Solution {
public List<Integer> diffWaysToCompute(String input) {
List<Integer> ret = new ArrayList<Integer>();
for(int i=0;i<input.length();i++){
int c = input.charAt(i);
if(c=='+' || c=='-' || c=='*') {
List<Integer> leftList = diffWaysToCompute(input.substring(0,i));
List<Integer> rightList = diffWaysToCompute(input.substring(i+1));
for(int left : leftList){
for(int right : rightList){
int t = 0;
switch(c){
case '+': t = left + right;
break;
case '-': t = left - right;
break;
case '*': t = left * right;
break;
}
ret.add(t);
}
}
}
}
if(ret.size()==0){
ret.add(Integer.valueOf(input));
}
return ret;
}
}LeetCode:Different Ways to Add Parentheses
原文：http://blog.csdn.net/itismelzp/article/details/51501257