Distinct

Compute number of distinct values in an array.

Write a function

func Solution(A []int) int

that, given an array A consisting of N integers, returns the number of distinct values in array A.

For example, given array A consisting of six elements such that:

A[0] = 2 A[1] = 1 A[2] = 1 A[3] = 2 A[4] = 3 A[5] = 1 the function should return 3, because there are 3 distinct values appearing in array A, namely 1, 2 and 3.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [0..100,000]; each element of array A is an integer within the range [−1,000,000..1,000,000]. Copyright 2009–2021 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

題目大意

返回不重複的整數數量

解題思路

1. 方法ㄧ: 先排序, 在檢查當前跟前一個是不是同一個整數. 不是的會結果+1
2. 方法二: 建立一個set. 最後返回set的長度

來源

https://app.codility.com/programmers/lessons/6-sorting/distinct/

解答

https://github.com/kimi0230/LeetcodeGolang/blob/master/Codility/Lesson/0006.Sorting/Distinct/Distinct.go

package Distinct

import "sort"

func Solution(A []int) int {
    sort.Ints(A)
    if len(A) == 0 {
        return 0
    }
    result := 1
    for i := 1; i < len(A); i++ {
        if A[i] != A[i-1] {
            result++
        }
    }
    return result
}

func SolutionSet(A []int) int {
    set := make(map[int]struct{})
    var void struct{}

    for i := 0; i < len(A); i++ {
        if _, ok := set[A[i]]; !ok {
            set[A[i]] = void
        }
    }
    return len(set)
}