leetcode 413. Arithmetic Slices | 413. 等差数列划分（Java）

短命女 2022-09-02 11:39 114阅读 0赞

## 题目 ##

[https://leetcode.com/problems/arithmetic-slices/][https_leetcode.com_problems_arithmetic-slices]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]

## 题解 ##

一次遍历搞定，直接看草稿。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]

class Solution { 
        public int numberOfArithmeticSlices(int[] nums) { 
            if (nums.length < 3) return 0;
            int sum = 0;
            int cnt = 0;
            int dif = nums[1] - nums[0]; // 上一个公差
            for (int i = 2; i < nums.length; i++) { 
                int newDif = nums[i] - nums[i - 1]; // 当前公差
                if (dif == newDif) { 
                    cnt++;
                } else { 
                    // 清算前一阶段
                    sum += cnt * (cnt + 1) / 2;
                    cnt = 0;
                    dif = newDif;
                }
            }
            // 清算末尾
            sum += cnt * (cnt + 1) / 2;
            return sum;
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 2]

[https_leetcode.com_problems_arithmetic-slices]: https://leetcode.com/problems/arithmetic-slices/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70]: /images/20220829/f49297e96ee34deb83a4061529652ae6.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 1]: /images/20220829/bce90b6cc2964be4950a16b14e7c36cf.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NpbmF0XzQyNDgzMzQx_size_16_color_FFFFFF_t_70 2]: /images/20220829/ecd202780e6d4c939afd5f32a9406a4e.png