LeetCode 1502. Can Make Arithmetic Progression From Sequence 解題紀錄

2020-03-30 170 words One minute

Contents

題目

Problem

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 $\leq$ arr.length $\leq$ 1000
$-10^6 \leq$ arr[i] $\leq 10^6$

想法

整組 vector 依照大小排列，兩兩檢查中間的間隙是否等大。

解法

bool canMakeArithmeticProgression(vector<int>& arr) {

    sort(arr.begin(), arr.end());

    auto t = arr[1] - arr[0];

    for(auto i=arr.size()-1; i>1; i--)
    {
        if(arr[i] - arr[i-1] != t)
        {
            return 0;
        }
    }

    return 1;
}

Time complexity: $\mathcal{O}(n)$.
Space complexity: $\mathcal{O}(1)$.