/**

public boolean isAdditiveNumber(String num) {

for (int i = 1; i <= num.length() / 2; i++) {

for (int j = 1; Math.max(i, j) <= num.length() - i - j; j++) {

if (isValid(i, j, num)) return true;

}

}

return false;

}

private boolean isValid(int i, int j, String num) {

if (num.charAt(0) == '0' && i > 1) return false;

if (num.charAt(i) == '0' && j > 1) return false;

String sum = "";

Long x1 = Long.parseLong(num.substring(0, i));

Long x2 = Long.parseLong(num.substring(i, i + j));

for (int start = i + j; start != num.length(); start += sum.length()) {

x2 = x2 + x1;

x1 = x2 - x1;

sum = x2.toString();

if (!num.startsWith(sum, start)) {

return false;

}

}

return true;

}