package main
import (
"fmt"
"math/rand"
"time"
)
/*
Goal:
- Select N random values that appear exactly once in the slice.
- The slice includes duplicates, but only values with frequency = 1
are eligible for selection.
Approach:
1. Count frequencies using a map[int]int.
2. Collect values that appear exactly once.
3. Shuffle the unique slice using rand.Shuffle.
4. Take the first N values.
5. Return them and print them.
Notes:
- Uses Go's built-in tools for clarity and efficiency.
- Uses structured, expressive functions.
*/
//---------------------------------------------------------------
// Build a frequency map: value -> count
//---------------------------------------------------------------
func buildFrequencyMap(data []int) map[int]int {
freq := make(map[int]int)
for _, value := range data {
freq[value]++
}
return freq
}
//---------------------------------------------------------------
// Collect values that appear exactly once
//---------------------------------------------------------------
func collectGloballyUniqueValues(data []int, freq map[int]int) []int {
unique := make([]int, 0)
for _, value := range data {
if freq[value] == 1 {
unique = append(unique, value)
}
}
return unique
}
//---------------------------------------------------------------
// Randomly select N values from the unique slice
//---------------------------------------------------------------
func selectRandomUnique(unique []int, N int) []int {
if N > len(unique) {
N = len(unique) // clamp
}
// Shuffle using Fisher–Yates via rand.Shuffle
temp := make([]int, len(unique))
copy(temp, unique)
rand.Shuffle(len(temp), func(i, j int) {
temp[i], temp[j] = temp[j], temp[i]
})
return temp[:N]
}
//---------------------------------------------------------------
// Print helper
//---------------------------------------------------------------
func printSlice(slice []int) {
for _, v := range slice {
fmt.Printf("%d ", v)
}
fmt.Println()
}
//---------------------------------------------------------------
// Main program
//---------------------------------------------------------------
func main() {
rand.Seed(time.Now().UnixNano())
// Example slice with duplicates
data := []int{
5, 12, 5, 19, 5, 33, 19, 5, 8, 8, 8, 59, 61, 17, 3, 5, 3, 74, 83, 90, 3, 1,
}
// Step 1: Build frequency map
freq := buildFrequencyMap(data)
// Step 2: Collect values that appear exactly once
uniqueValues := collectGloballyUniqueValues(data, freq)
// Step 3: Choose how many unique random values to select
N := 5
// Step 4: Select N random unique values
randomSelection := selectRandomUnique(uniqueValues, N)
// Step 5: Print results
fmt.Println("Values that appear exactly once:")
printSlice(uniqueValues)
fmt.Printf("\nRandom selection (%d values):\n", N)
printSlice(randomSelection)
}
/*
run:
Values that appear exactly once:
12 33 59 61 17 74 83 90 1
Random selection (5 values):
90 83 33 17 61
*/
