public List<Integer> diffWaysToCompute(String input) {

List<Integer> result = new ArrayList<Integer>();

int k = 0;

int curr = 0;

while (k < input.length() && Character.isDigit(input.charAt(k))) {

curr = curr * 10 + (int)input.charAt(k) - (int)'0';

k += 1;

}

if (k == input.length()) {

result.add(curr);

return result;

}

for (int i = 0; i < input.length(); i++) {

if (Character.isDigit(input.charAt(i)) == false) {

List<Integer> left = diffWaysToCompute(input.substring(0, i));

List<Integer> right = diffWaysToCompute(input.substring(i+1, input.length()));

for (int m = 0; m < left.size(); m++) {

for (int n = 0; n < right.size(); n++) {

int op1 = left.get(m);

int op2 = right.get(n);

int r = 0;

char op = input.charAt(i);

if (op == '-') {

r = op1 - op2;

} else if (op == '+') {

r = op1 + op2;

} else {

r = op1 * op2;

}

result.add(r);

}

}

}

}

return result;

}