面试题44. 数字序列中某一位的数字

女爷i 2023-02-17 14:54 68阅读 0赞

# 题目： #

[面试题44. 数字序列中某一位的数字][44.]  
[400. 第N个数字][400. _N]  
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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]

# 题解： #

## 1. 解释一： ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 2]  
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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 9]  
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## 2. 解释二： ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 14]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 15]

# 代码： #

public class 面试题44 { 
    
        public static int findNthDigit(int n) { 
            int digit = 1;
            long start = 1;
            long count = 9;
            
            while(n > count) // 1.
            { 
                n -= count;
                digit += 1;
                start *= 10;
                count = 9 * start * digit;
            }
    
            long num = start + (n - 1) / digit; // 2.
            int res = Long.toString(num).charAt((n - 1) % digit) - '0'; // 3.
            return res;
        }
    
        public static void main(String[] args) { 
            int n1 = 3;
            int n2 = 11;
            int n3 = 15;
    
            int res1 = findNthDigit(n1);
            int res2 = findNthDigit(n2);
            int res3 = findNthDigit(n3);
    
            System.out.println(res1);
            System.out.println(res2);
            System.out.println(res3);
        }
    }

# 参考： #

1.  [面试题44. 数字序列中某一位的数字（迭代 + 求整 / 求余，清晰图解）][44. _ _ _ _]
2.  [详解 找规律][Link 1]

[44.]: https://leetcode-cn.com/problems/shu-zi-xu-lie-zhong-mou-yi-wei-de-shu-zi-lcof/
[400. _N]: https://leetcode-cn.com/problems/nth-digit/
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[44. _ _ _ _]: https://leetcode-cn.com/problems/shu-zi-xu-lie-zhong-mou-yi-wei-de-shu-zi-lcof/solution/mian-shi-ti-44-shu-zi-xu-lie-zhong-mou-yi-wei-de-6/
[Link 1]: https://leetcode-cn.com/problems/shu-zi-xu-lie-zhong-mou-yi-wei-de-shu-zi-lcof/solution/zhe-shi-yi-dao-shu-xue-ti-ge-zhao-gui-lu-by-z1m/