1502. Can Make Arithmetic Progression From Sequence

🟩 Easy

A sequence of numbers is called an arithmetic progression if the difference between any two consecutive elements is the same.

Given an array of numbers arr, return true if the array can be rearranged to form an arithmetic progression. Otherwise, return false.

Example 1

Input: arr = [3,5,1] Output: true Explanation: We can reorder the elements as [1,3,5] or [5,3,1] with differences 2 and -2 respectively, between each consecutive elements.

Example 2

Input: arr = [1,2,4] Output: false Explanation: There is no way to reorder the elements to obtain an arithmetic progression.

Constraints

• 2 <= arr.length <= 1000

• -10^6 <= arr[i] <= 10^6

Hint-1

Consider that any valid arithmetic progression will be in sorted order.

Hint-2

Sort the array, then check if the differences of all consecutive elements are equal.

Solution

My Solution

func canMakeArithmeticProgression(arr []int) bool {
    sort.Ints(arr)
    d := arr[1] - arr[0]

    for i:=2; i<len(arr); i++ {
        if arr[i]-arr[i-1] != d {
            return false
        }
    }

    return true
}

Optimal solution

func canMakeArithmeticProgression(arr []int) bool {
    n := len(arr)
    if n < 2 {
        return true
    }
    
    // Find min and max
    min, max := arr[0], arr[0]
    for _, num := range arr {
        if num < min {
            min = num
        }
        if num > max {
            max = num
        }
    }
    
    // Check if difference is integer
    diff := (max - min) / (n - 1)
    if (max-min)%(n-1) != 0 {
        return false
    }
    
    // Use a set to track elements
    seen := make(map[int]bool)
    for _, num := range arr {
        if (num-min)%diff != 0 {
            return false
        }
        seen[num] = true
    }
    
    return len(seen) == n
}

result

Leetcode: link