413. Arithmetic Slices¶

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413. Arithmetic Slices

Medium

An integer array is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.

• For example, [1,3,5,7,9], [7,7,7,7], and [3,-1,-5,-9] are arithmetic sequences.

Given an integer array nums, return the number of arithmetic subarrays of nums.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: nums = [1,2,3,4]
Output: 3
Explanation: We have 3 arithmetic slices in nums: [1, 2, 3], [2, 3, 4] and [1,2,3,4] itself.

Example 2:

Input: nums = [1]
Output: 0

Constraints:

• 1 <= nums.length <= 5000
• -1000 <= nums[i] <= 1000

Solution¶

class Solution {
    public int numberOfArithmeticSlices(int[] nums) {
        int n = nums.length;
        int count = 0;
        for (int i = 0; i < n; i++) {
            ArrayList<Integer> temp = new ArrayList<>();
            for (int j = i; j < n; j++) {
                temp.add(nums[j]);
                if (check(temp) == true) count++;
            }
        }
        return count;
    }
    private boolean check(ArrayList<Integer> res) {
        int n = res.size();
        if (n < 3) return false;
        int diff = res.get(1) - res.get(0);
        for (int i = 0; i < n - 1; i++) {
            int next = res.get(i + 1);
            int current = res.get(i);
            if (next - current != diff) return false;
        }
        return true;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here