diff --git a/20201229/main.go b/20201229/main.go
new file mode 100644
index 0000000..a511c2e
--- /dev/null
+++ b/20201229/main.go
@@ -0,0 +1,27 @@
+package main
+
+func main() {
+
+}
+
+func isEqual(s, t string) bool {
+	return process(s) == process(t)
+}
+
+func process(s string) string {
+	var ret []rune
+	for _, c := range s {
+		if string(c) == "#" {
+			if len(ret) > 0 {
+				ret = ret[:len(ret)-1]
+			}
+			continue
+		}
+		ret = append(ret, c)
+	}
+	return string(ret)
+}
+
+func process2(s string) string {
+	return ""
+}
diff --git a/20201229/main_test.go b/20201229/main_test.go
new file mode 100644
index 0000000..4d3be7b
--- /dev/null
+++ b/20201229/main_test.go
@@ -0,0 +1,122 @@
+package main
+
+import "testing"
+
+func Test_process(t *testing.T) {
+	type args struct {
+		s string
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			"test1",
+			args{"ab#c"},
+			"ac",
+		},
+		{
+			"test2",
+			args{"ad#c"},
+			"ac",
+		},
+		{
+			"test3",
+			args{"ab##"},
+			"",
+		},
+		{
+			"test4",
+			args{"c#d#"},
+			"",
+		},
+		{
+			"test5",
+			args{"a##c"},
+			"c",
+		},
+		{
+			"test6",
+			args{"#a#c"},
+			"c",
+		},
+		{
+			"test7",
+			args{"a#c"},
+			"c",
+		},
+		{
+			"test8",
+			args{"b"},
+			"b",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := process(tt.args.s); got != tt.want {
+				t.Errorf("process() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_isEqual(t *testing.T) {
+	type args struct {
+		s string
+		t string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"test1",
+			args{
+				"ab#c",
+				"ad#c",
+			},
+			true,
+		},
+		{
+			"test2",
+			args{
+				"ab##",
+				"c#d#",
+			},
+			true,
+		},
+		{
+			"test3",
+			args{
+				"a##c",
+				"#a#c",
+			},
+			true,
+		},
+		{
+			"test3",
+			args{
+				"a#c",
+				"b",
+			},
+			false,
+		},
+		{
+			"test4",
+			args{
+				"ac##",
+				"a##",
+			},
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isEqual(tt.args.s, tt.args.t); got != tt.want {
+				t.Errorf("isEqual() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}