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leetcode306.java
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leetcode306.java
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/*
Reference: https://leetcode.com/discuss/71455/java-very-straightforward-solution-detailed-explanation
*/
public class Solution {
public boolean isAdditiveNumber(String num) {
int len = num.length();
for(int i = 1; i <= (len-1)/2; i++){
if(num.charAt(0) == '0' && i >= 2)
break;
for(int j = i+1; len-j >= j-i && len - j >= i; j++){
if(num.charAt(i) == '0' && j-i >= 2)
break;
long num1 = Long.parseLong(num.substring(0,i)); //num1
long num2 = Long.parseLong(num.substring(i,j)); //num2
String substr = num.substring(j); //rest
if(isAdditive(substr, num1, num2))
return true;
}
}
return false;
}
private boolean isAdditive(String str, long a, long b){
if(str.equals(""))
return true; //reach the end of string
long sum = a + b;
String s = ((Long)sum).toString();
if(!str.startsWith(s))
return false;
return isAdditive(str.substring(s.length()), b, sum);
}
}