*** disclaimer : i'm not a professional developer, been tinkering with golang for about 8 month (udemy + youtube) and still got no idea how to simple problem like below..
Here's the summarize of the problem :
I'm trying to find the most frequent "age" from struct that comes from the decoded .json file (containing string "name" and integer "age").
After that i need to print the "name" based on the maximum occurence frequency of "age".
The printed "name" based on the maximum-occurence of "age" needs to be sorted alpabethically
Input (.json) :
[
{"name": "John","age": 15},
{"name": "Peter","age": 12},
{"name": "Roger","age": 12},
{"name": "Anne","age": 44},
{"name": "Marry","age": 15},
{"name": "Nancy","age": 15}
]
Output : ['John', 'Mary', 'Nancy'].
Explaination : Because the most occurring age in the data is 15 (occured 3 times), the output should be an array of strings with the three people's name, in this case it should be ['John', 'Mary', 'Nancy'].
Exception :
This is what i've tried (in Golang) :
package main
{
import (
"encoding/json"
"fmt"
"os"
"sort"
)
// 1. preparing the empty struct for .json
type Passanger struct {
Name string `json:"name"`
Age int `json:"age"`
}
func main() {
// 2. load the json file
content, err := os.ReadFile("passanger.json")
if err != nil {
fmt.Println(err.Error())
}
// 3. parse json file to slice
var passangers []Passanger
err2 := json.Unmarshal(content, &passangers)
if err2 != nil {
fmt.Println("Error JSON Unmarshalling")
fmt.Println(err2.Error())
}
// 4. find most frequent age numbers (?)
for _, v := range passangers {
// this code only show the Age on every line
fmt.Println(v.Age)
}
// 5. print the name and sort them apabethically (?)
// use sort.slice package
// implement group based by "max-occurence-age"
}
Been stuck since yesterday, i've also tried to implement the solution from many coding challenge question like :
func majorityElement(arr int) int {
sort.Ints(arr)
return arr[len(arr)/2]
}
but i'm still struggling to understand how to handle the "age" value from the Passanger slice as an integer input(arr int) to code above.
others solution i've found online is by iterating trough map[int]int to find the maximum frequency :
func main(){
arr := []int{90, 70, 30, 30, 10, 80, 40, 50, 40, 30}
freq := make(map[int]int)
for _ , num := range arr {
freq[num] = freq[num]+1
}
fmt.Println("Frequency of the Array is : ", freq)
}
but then again, the .json file contain not only integer(age) but also string(name) format, i still don't know how to handle the "name" and "age" separately..
i really need a proper guidance here.
*** here's the source code (main.go) and (.json) file that i mentioned above : https://github.com/ariejanuarb/golang-json
During my first years of college, my teachers would always repeat something to me and my fellow classmates, don't write code first, especially if you are a beginner, follow these steps instead:
Let's follow these steps...
You have well defined your problem so i will skip this step.
There might more scenario but they are yours to find
Well now that we have found out what we must be doing, we are going to check the input and output of each steps to achieve this goal.
the steps:
The first type, the one inside the bracket is the age of the whole group.
The second type, is a list that contains either:
it is not important as long as we can retrieve back easily the passenger from the list without iterating it back again.
so here we have scenario 1 and 2 branching out... which mean that it must either be valid for all scenario or use a condition to branch them out.
we can see that the output for scenario 1 can be merged with the output of scenario 2
You want to print the name in alphabetical order of all passengers in an ageGroup
to be honest, you can skip this one if you want to.
let's create functions that fit our signature first
type Passenger struct {
Name string `json:"name"`
Age int `json:"age"`
}
func GetPassengerList() []Passenger{
// 2. load the json file
content, err := os.ReadFile("passanger.json")
if err != nil {
fmt.Println(err.Error())
}
// 3. parse json file to slice
var passengers []Passenger
err2 := json.Unmarshal(content, &passengers)
if err2 != nil {
fmt.Println("Error JSON Unmarshalling")
fmt.Println(err2.Error())
}
return passengers
}
// 4a. Group by Age
func GroupByAge(passengers []Passenger) map[int][]int {
group := make(map[int][]int, 0)
for index, passenger := range passengers {
ageGroup := group[passenger.Age]
ageGroup = append(ageGroup, index)
group[passenger.Age] = ageGroup
}
return group
}
// 4b. find the most frequent age numbers
func FindMostCommonAge(ageGroups map[int][]int) []int {
mostFrequentAges := make([]int, 0)
biggestGroupSize := 0
// find most frequent age numbers
for age, ageGroup := range ageGroups {
// is most frequent age
if biggestGroupSize < len(ageGroup) {
biggestGroupSize = len(ageGroup)
mostFrequentAges = []int{age}
} else if biggestGroupSize == len(ageGroup) { // is one of the most frequent age
mostFrequentAges = append(mostFrequentAges, age)
}
// is not one of the most frequent age so does nothing
}
return mostFrequentAges
}
func main() {
passengers := loadPassengers()
// I am lazy but if you want you could sort the
// smaller slice before printing to increase performance
sort.Slice(passengers, func(i, j int) bool {
if passengers[i].Age == passengers[j].Age {
return passengers[i].Name < passengers[j].Name
}
return passengers[i].Age < passengers[j].Age
})
// age => []position
// Length of the array count as the number of occurences
ageGrouper := GroupByAge(passengers)
mostFrequentAges := FindMostCommonAge(ageGrouper)
// print the passenger
for _, age := range mostFrequentAges {
fmt.Println("{")
for _, passengerIndex := range ageGrouper[age] {
fmt.Println("\t", passengers[passengerIndex].Name)
}
fmt.Println("}")
}
}