feat: add map methods.

hashmap.go

@@ -80,11 +80,32 @@ func (m *HashMap[K, V]) Get(k K) (V, bool) {
 	return v, ok
 }
 
+// GetDefault returns the value associated with the specified key, and returns the default value if
+// this map contains no pair with the key.
+func (m *HashMap[K, V]) GetDefault(k K, defaultVal V) V {
+	v, ok := (*m)[k]
+	if !ok {
+		return defaultVal
+	}
+
+	return v
+}
+
 // IsEmpty returns true if this map is empty.
 func (m *HashMap[K, V]) IsEmpty() bool {
 	return m.Size() == 0
 }
 
+// Keys returns a slice that contains all the keys in this map.
+func (m *HashMap[K, V]) Keys() []K {
+	keys := make([]K, 0, len(*m))
+	for k := range *m {
+		keys = append(keys, k)
+	}
+
+	return keys
+}
+
 // Put associate the specified value with the specified key in this map.
 func (m *HashMap[K, V]) Put(k K, v V) V {
 	old := (*m)[k]
@@ -101,7 +122,30 @@ func (m *HashMap[K, V]) Remove(k K) V {
 	return old
 }
 
+// Replace replaces the value for the specified key only if it is currently in this map.
+func (m *HashMap[K, V]) Replace(k K, v V) (V, bool) {
+	old, ok := (*m)[k]
+	if !ok {
+		return old, false // zero value
+	}
+
+	(*m)[k] = v
+
+	return old, true
+}
+
 // Size returns the number of key-value pairs in this map.
 func (m *HashMap[K, V]) Size() int {
 	return len(*m)
 }
+
+// Values returns a slice that contains all the values in this map.
+func (m *HashMap[K, V]) Values() []V {
+	arr := make([]V, 0, len(*m))
+
+	for _, v := range *m {
+		arr = append(arr, v)
+	}
+
+	return arr
+}

map.go

@@ -20,15 +20,28 @@ type Map[K comparable, V any] interface {
 	// Get returns the value which associated to the specified key.
 	Get(k K) (V, bool)
 
+	// GetDefault returns the value associated with the specified key, and returns the default value
+	// if this map contains no pair with the key.
+	GetDefault(k K, defaultVal V) V
+
 	// IsEmpty returns true if this map is empty.
 	IsEmpty() bool
 
+	// Keys returns a slice that contains all the keys in this map.
+	Keys() []K
+
 	// Put associate the specified value with the specified key in this map.
 	Put(k K, v V) V
 
 	// Remove removes the key-value pair with the specified key.
 	Remove(k K) V
 
+	// Replace replaces the value for the specified key only if it is currently in this map.
+	Replace(k K, v V) (V, bool)
+
 	// Size returns the number of key-value pairs in this map.
 	Size() int
+
+	// Values returns a slice that contains all the values in this map.
+	Values() []V
 }

map_test.go

@@ -44,6 +44,19 @@ func testMapGet(t *testing.T, m Map[int, int], data []int) {
 			}
 		}
 	}
+
+	for i := 0; i < len(data)*2; i++ {
+		v := m.GetDefault(i, i+1)
+		if i < len(data) {
+			if v != data[i] {
+				t.Errorf("HashMap.GetDefault(%d) returns %d, expect %d", i, v, data[i])
+			}
+		} else {
+			if v != i+1 {
+				t.Errorf("HashMap.GetDefault(%d) returns %d, expect %d", i, v, i+1)
+			}
+		}
+	}
 }
 
 func testMapContains(t *testing.T, m Map[int, int], data []int) {