LeetCode0241.java

/* Different Ways to Add Parentheses
 * 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
 * */

import java.util.ArrayList;
import java.util.List;

public class LeetCode0241 {
    public static void main(String[] args) {
        String input = "2-1-1";
        System.out.println(diffWaysToCompute(input));
    }

    public static 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 == '*') {
                List<Integer> left = diffWaysToCompute(input.substring(0, i));  // substring截取至第i-1个
                List<Integer> right = diffWaysToCompute(input.substring(i + 1));
                for (int l : left) {
                    for (int r : right) {
                        switch (c) {
                            case '+':
                                res.add(l + r);
                                break;
                            case '-':
                                res.add(l - r);
                                break;
                            case '*':
                                res.add(l * r);
                                break;
                        }
                    }
                }
            }
        }

        if (res.isEmpty())
            res.add(Integer.valueOf(input));

        return res;
    }
}