Algorithm
Problem Name: 413. Arithmetic Slices
Problem Link: https://leetcode.com/problems/arithmetic-slices/
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
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
class Solution {
public int numberOfArithmeticSlices(int[] nums) {
int[] dp = new int[nums.length];
int count = 0;
for (int i = 2; i < dp.length; i++) {
if (nums[i] - nums[i - 1] == nums[i - 1] - nums[i - 2]) {
dp[i] = dp[i - 1] + 1;
count += dp[i];
}
}
return count;
}
}
Input
nums = [1,2,3,4]
Output
3
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const numberOfArithmeticSlices = function(A) {
const arr = [];
let count = 0;
for (let i = 1; i < A.length - 1; i++) {
if (A[i] - A[i - 1] === A[i + 1] - A[i]) {
count += 1;
} else {
arr.push(count);
count = 0;
}
}
arr.push(count);
return arr.reduce((ac, el) => ac + calc(el), 0);
};
function calc(num) {
return (num * (num + 1)) / 2;
}
console.log(numberOfArithmeticSlices([1, 2, 3, 4]));
Input
nums = [1,2,3,4]
Output
3