Arithmetic slices

Array Dynamic Programming Sliding Window

64.8% acceptance

Jan 13, 2026

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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.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn number_of_arithmetic_slices(nums: Vec<i32>) -> i32 {
    if nums.len() < 3 {
      return 0;
    }
    
    let mut count = 0;
    let mut current = 0;
    
    for i in 2..nums.len() {
      if nums[i] - nums[i - 1] == nums[i - 1] - nums[i - 2] {
        current += 1;
        count += current;
      } else {
        current = 0;
      }
    }
    
    count
  }
}