impl: q238, q380

solutions/q238/solution.go

@@ -0,0 +1,24 @@
+package q238
+
+func productExceptSelf(nums []int) []int {
+	ret := make([]int, len(nums))
+
+	// from left
+	t := 1
+	for i := range len(nums) - 1 {
+		t *= nums[i]
+		ret[i+1] = t
+	}
+	ret[0] = 1
+
+	// from right
+	t = 1
+	for i := len(nums) - 1; i > 0; i-- {
+		t *= nums[i]
+		ret[i-1] *= t
+	}
+
+	return ret
+}
+
+var _ = productExceptSelf

solutions/q238/solution_test.go

@@ -0,0 +1,32 @@
+package q238
+
+import (
+	"slices"
+	"testing"
+)
+
+func Test_productExceptSelf(t *testing.T) {
+	tests := []struct {
+		name string // description of this test case
+		// Named input parameters for target function.
+		nums []int
+		want []int
+	}{
+		{
+			nums: []int{1, 2, 3, 4},
+			want: []int{24, 12, 8, 6},
+		},
+		{
+			nums: []int{-1, 1, 0, -3, 3},
+			want: []int{0, 0, 9, 0, 0},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := productExceptSelf(tt.nums)
+			if !slices.Equal(got, tt.want) {
+				t.Errorf("productExceptSelf() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

solutions/q380/solution.go

@@ -0,0 +1,69 @@
+package q380
+
+import (
+	"math/rand"
+	"runtime/debug"
+)
+
+func init() {
+	debug.SetMemoryLimit(16 << 20)
+}
+
+var rng *rand.Rand = rand.New(rand.NewSource(42))
+
+type RandomizedSet struct {
+	vals []int
+	idx  map[int]int // the index of the element in vals
+}
+
+func Constructor() RandomizedSet {
+	return RandomizedSet{
+		vals: []int{},
+		idx:  map[int]int{},
+	}
+}
+
+// Insert Inserts an item val into the set if not present. Returns true if the
+// item was not present, false otherwise.
+func (rs *RandomizedSet) Insert(val int) bool {
+	if _, present := rs.idx[val]; present {
+		return false
+	}
+	rs.idx[val] = len(rs.vals)
+	rs.vals = append(rs.vals, val)
+	return true
+}
+
+// Remove Removes an item val from the set if present. Returns true if the item
+// was present, false otherwise.
+func (rs *RandomizedSet) Remove(val int) bool {
+	idx, present := rs.idx[val]
+	if !present {
+		return false
+	}
+	delete(rs.idx, val)
+
+	idxLast := len(rs.vals) - 1
+	if idx != idxLast {
+		rs.vals[idx] = rs.vals[idxLast]
+		rs.idx[rs.vals[idx]] = idx
+	}
+	rs.vals = rs.vals[:idxLast]
+	return true
+}
+
+// GetRandom Returns a random element from the current set of elements (it's
+// guaranteed that at least one element exists when this method is called).
+// Each element must have the same probability of being returned.
+func (rs *RandomizedSet) GetRandom() int {
+	i := rng.Intn(len(rs.vals))
+	return rs.vals[i]
+}
+
+/**
+ * Your RandomizedSet object will be instantiated and called as such:
+ * obj := Constructor();
+ * param_1 := obj.Insert(val);
+ * param_2 := obj.Remove(val);
+ * param_3 := obj.GetRandom();
+ */