Sort a Map by Its Values

📌 Definition:

📖 Detailed Explanation:

A hash map is unordered, so extract the entries, sort them by value with a comparator (reversed for descending, with a tie-break on the key), and collect into an insertion-ordered structure. The common mistake is expecting the hash map itself to become sorted. O(k log k).

💻 Solutions:

• Java
• JavaScript
• Python

public static Map<String,Integer> sortByValueDesc(Map<String,Integer> map) {
    return map.entrySet().stream()
        .sorted(Map.Entry.<String,Integer>comparingByValue().reversed())
        .collect(java.util.stream.Collectors.toMap(
            Map.Entry::getKey, Map.Entry::getValue,
            (a, b) -> a, LinkedHashMap::new));
}

function sortByValueDesc(obj) {
  return Object.entries(obj)
    .sort((a, b) => b[1] - a[1])
    .reduce((acc, [k, v]) => (acc[k] = v, acc), {});
}

def sort_by_value_desc(d):
    return dict(sorted(d.items(), key=lambda kv: kv[1], reverse=True))

🔑 Key Points:

• Hash map is unordered — build an ordered result
• Sort entries by value, tie-break on key
• Collect into an insertion-ordered map/list
• O(k log k)

🌍 Real-World Example: