资讯专栏INFORMATION COLUMN

[LeetCode] Additive Number

yibinnn / 3107人阅读

Additive Number

Additive number is a string whose digits can form additive sequence.

A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two.

For example:
"112358" is an additive number because the digits can form an additive sequence: 1, 1, 2, 3, 5, 8.

1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8
"199100199" is also an additive number, the additive sequence is: 1, 99, 100, 199.
1 + 99 = 100, 99 + 100 = 199
Note: Numbers in the additive sequence cannot have leading zeros, so sequence 1, 2, 03 or 1, 02, 3 is invalid.

Given a string containing only digits "0"-"9", write a function to determine if it"s an additive number.

Follow up:
How would you handle overflow for very large input integers?

Note

Here is my thought:
you get two consecutive substrings with two for loops, then call a recursive function to check whether the rest string starts with the sum of them.

Solution
public class Solution {
    public boolean isAdditiveNumber(String num) {
        int n = num.length();
        for (int i = 1; i <= (n-1)/2; i++) {
            if (num.charAt(0) == "0" && i > 1) break;
            for (int j = i+1; j-i <= n-j && i <= n-j; j++) {
                if (num.charAt(i) == "0" && j > i+1) break;
                long num1 = Long.parseLong(num.substring(0,i));
                long num2 = Long.parseLong(num.substring(i,j));
                String substr = num.substring(j);
                if (isValid(num1, num2, substr)) return true;
            }
        }
        return false;
    }
    public boolean isValid(long num1, long num2, String str) {
        if (str.equals("")) return true;
        long sum = num1+num2;
        String s = ((Long)sum).toString();
        if (!str.startsWith(s)) return false;
        return isValid(num2, sum, str.substring(s.length()));
    }
}

文章版权归作者所有,未经允许请勿转载,若此文章存在违规行为,您可以联系管理员删除。

转载请注明本文地址:https://www.ucloud.cn/yun/66232.html

相关文章

  • leetcode306. Additive Number

    摘要:为了减少无效遍历,我们可以在寻找第一个数字和第二个数字的时候及时终止。我们可以知道第一个数字的长度不应该超过字符串长度的一般,第二个数字的长度无法超过字符串长度减去第一个数字的长度。因此一旦遇到,在判断完作为加数时是否合法后,直接跳出循环。 题目要求 Additive number is a string whose digits can form additive sequence....

    2shou 评论0 收藏0
  • LeetCode 306. Additive Number

    摘要:描述累加数是一个字符串,组成它的数字可以形成累加序列。一个有效的累加序列必须至少包含个数。说明累加序列里的数不会以开头,所以不会出现或者的情况。示例输入输出解释累加序列为。 LeetCode 306. Additive Number Description Additive number is a string whose digits can form additive sequen...

    GeekQiaQia 评论0 收藏0
  • 306. Additive Number

    摘要:题目解答不越界长度的当可以走到后面没有和了的时候,说明这个满足条件直接可以知道这个是不是存在于中越界长度的越界长的度 题目:Additive number is a string whose digits can form additive sequence. A valid additive sequence should contain at least three numbers...

    dkzwm 评论0 收藏0
  • 306. Additive Number

    For example: 112358 is an additive number because the digits can form an additive sequence: 1, 1, 2, 3, 5, 8. 1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8 199100199 is also an additive number, the addi...

    eccozhou 评论0 收藏0

发表评论

0条评论

yibinnn

|高级讲师

TA的文章

阅读更多
最新活动
阅读需要支付1元查看
<