package main
import (
"fmt"
"sort"
)
/*
FUNCTION: getRanks
-------------------
This function takes a slice of numbers and returns a slice of ranks.
Ranking rules used (Competition Ranking):
-----------------------------------------
- Highest value gets rank 1
- Equal values get the same rank
- Next rank increases by the number of equal values
Example:
Values: 88, 4, 19, 4, 1, 31, 14, 1, 93, 17
Ranks: 2, 7, 4, 7, 9, 3, 6, 9, 1, 5
Steps:
1. Make a sorted copy of the slice (descending)
2. Assign ranks to each unique value
3. Build a rank slice matching the original order
*/
func getRanks(slice []int) []int {
// Step 1: Create a sorted copy (descending)
sorted := make([]int, len(slice))
copy(sorted, slice)
sort.Slice(sorted, func(i, j int) bool {
return sorted[i] > sorted[j] // descending
})
// Step 2: Map each unique value to its rank
rankMap := make(map[int]int)
rank := 1
for _, value := range sorted {
// Assign rank only once per unique value
if _, exists := rankMap[value]; !exists {
rankMap[value] = rank
}
rank++ // next rank position
}
// Step 3: Build ranking slice in original order
ranks := make([]int, len(slice))
for i, value := range slice {
ranks[i] = rankMap[value]
}
return ranks
}
/*
FUNCTION: printRanking
-----------------------
Prints the original slice and its ranking.
*/
func printRanking(slice []int, ranks []int) {
fmt.Print("Original slice: [ ")
for _, v := range slice {
fmt.Print(v, " ")
}
fmt.Println("]")
fmt.Print("Ranking slice : [ ")
for _, r := range ranks {
fmt.Print(r, " ")
}
fmt.Println("]")
}
// MAIN PROGRAM
// ---------------------------------------------
func main() {
// slice
slice := []int{88, 4, 19, 4, 1, 31, 14, 1, 93, 17}
// Compute ranks
rankingSlice := getRanks(slice)
printRanking(slice, rankingSlice)
}
/*
run:
Original slice: [ 88 4 19 4 1 31 14 1 93 17 ]
Ranking slice : [ 2 7 4 7 9 3 6 9 1 5 ]
*/
