Add solution for Challenge 22 by Kosench

[Kosench]

Challenge 22 Solution

Submitted by: @Kosench
Challenge: Challenge 22

Description

This PR contains my solution for Challenge 22.

Changes

• Added solution file to challenge-22/submissions/Kosench/solution-template.go

Testing

• Solution passes all test cases
• Code follows Go best practices

Thank you for reviewing my submission! 🚀

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 33852238-85f7-4c45-ba4d-0d2956c9cfde

📥 Commits

Reviewing files that changed from the base of the PR and between f8d8930 and bb5101b.

📒 Files selected for processing (1)

• challenge-22/submissions/Kosench/solution-template.go

🚧 Files skipped from review as they are similar to previous changes (1)

• challenge-22/submissions/Kosench/solution-template.go

---

Walkthrough

Adds a Go solution file for Challenge 22 with greedy coin-change functions and a sample main that prints results for fixed amounts using U.S. denominations.

Changes

Greedy Coin-Change Solution

Layer / File(s)	Summary
Greedy coin-change functions challenge-22/submissions/Kosench/solution-template.go	Defines MinCoins and CoinCombination using sorted descending denominations, with -1/empty-map handling when an amount cannot be formed exactly.
Demo entrypoint challenge-22/submissions/Kosench/solution-template.go	Adds main that iterates sample amounts, calls both functions, and prints the outputs.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• RezaSi/go-interview-practice#577: Adds the same Challenge 22 greedy MinCoins/CoinCombination implementation pattern in a separate submission.
• RezaSi/go-interview-practice#1397: Adds the same exported functions for Challenge 22 with coin-exchange logic and map-based breakdown output.
• RezaSi/go-interview-practice#1738: Adds matching greedy MinCoins/CoinCombination logic with the same -1/empty-map remainder handling.

Poem

I’m a bunny with a coin-count grin,
Hop, sort, and pick the biggest in.
Quarters first, then dimes do gleam,
Tiny pennies finish the stream.
🐇🪙

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: adding a solution for Challenge 22 by Kosench.
Description check	✅ Passed	The description is directly related to the submitted Challenge 22 solution and its testing.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

---

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

challenge-22/submissions/Kosench/solution-template.go (1)

29-58: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Extract shared greedy logic to reduce duplication.

MinCoins and CoinCombination contain nearly identical greedy loops (lines 41-51 and 72-82). Extracting a shared helper that returns both the total count and the denomination-to-count map would eliminate duplication and ensure both functions stay in sync if the algorithm changes.

♻️ Proposed refactor: shared greedy helper

+// greedyBreakdown runs the greedy coin-selection and returns the total coin
+// count and a denomination-to-count map. If the amount cannot be made, count is -1
+// and the map is empty.
+func greedyBreakdown(amount int, denominations []int) (int, map[int]int) {
+	combo := make(map[int]int)
+	if amount < 0 {
+		return -1, combo
+	}
+	remaining := amount
+	totalCoins := 0
+
+	sorted := make([]int, len(denominations))
+	copy(sorted, denominations)
+	sort.Ints(sorted)
+
+	for i := len(sorted) - 1; i >= 0; i-- {
+		coin := sorted[i]
+		if coin > 0 && coin <= remaining {
+			count := remaining / coin
+			combo[coin] = count
+			totalCoins += count
+			remaining %= coin
+		}
+		if remaining == 0 {
+			break
+		}
+	}
+	if remaining > 0 {
+		return -1, make(map[int]int)
+	}
+	return totalCoins, combo
+}
+
 func MinCoins(amount int, denominations []int) int {
-	if amount < 0 {
-		return -1
-	}
-	if amount == 0 {
-		return 0
-	}
-
-	totalCoins := 0
-	remaining := amount
-
-	for i := len(denominations) - 1; i >= 0; i-- {
-		coin := denominations[i]
-		if coin > 0 && coin <= remaining {
-			count := remaining / coin
-			totalCoins += count
-			remaining %= coin
-		}
-		if remaining == 0 {
-			break
-		}
-	}
-
-	if remaining > 0 {
-		return -1
-	}
-	return totalCoins
+	count, _ := greedyBreakdown(amount, denominations)
+	if amount == 0 {
+		return 0
+	}
+	return count
 }

 func CoinCombination(amount int, denominations []int) map[int]int {
-	combo := make(map[int]int)
-	if amount < 0 {
-		return combo
-	}
-
-	remaining := amount
-
-	for i := len(denominations) - 1; i >= 0; i-- {
-		coin := denominations[i]
-		if coin > 0 && coin <= remaining {
-			count := remaining / coin
-			combo[coin] = count
-			remaining %= coin
-		}
-		if remaining == 0 {
-			break
-		}
-	}
-
-	if remaining > 0 {
-		return make(map[int]int)
-	}
-	return combo
+	_, combo := greedyBreakdown(amount, denominations)
+	return combo
 }

Also applies to: 64-88

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b72cdab8-3c18-446e-9f9b-669e729335fd

📥 Commits

Reviewing files that changed from the base of the PR and between f5e7ce5 and f8d8930.

📒 Files selected for processing (1)

• challenge-22/submissions/Kosench/solution-template.go

[github-actions]

🎉 Auto-merged!

This PR was automatically merged after 2 days with all checks passing.

Thank you for your contribution, @Kosench!

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