diff --git a/Week_04/id_40/LeetCode_169_040.go b/Week_04/id_40/LeetCode_169_040.go
new file mode 100644
index 00000000..83c0f3de
--- /dev/null
+++ b/Week_04/id_40/LeetCode_169_040.go
@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+// 快速排序
+func qsort(arr []int) []int {
+	if len(arr) < 2 {
+		return arr
+	} else {
+		pivot := arr[0]
+		var less []int
+		var greater []int
+		for _, value := range arr[1:] {
+			if value <= pivot {
+				less = append(less, value)
+			} else {
+				greater = append(greater, value)
+			}
+		}
+		var result []int
+		result = append(result, qsort(less)...)
+		result = append(result, pivot)
+		result = append(result, qsort(greater)...)
+		return result
+	}
+}
+
+//给数组排个序，因为众数数目大于全部数字数目的一半，直接返回中位数就行
+func majorityElement(nums []int) int {
+	//quick_sort(nums, 0, len(nums)-1)
+	//nums = qsort(nums)
+	sort.Ints(nums)
+	return nums[len(nums)/2]
+}
+
+func main() {
+	test := []int{5, 3, 2, 4, 1, 6, 7}
+	quick_sort(test, 0, len(test)-1)
+	fmt.Println(majorityElement(test), "======")
+	test = []int{3, 3, 2}
+	quick_sort(test, 0, len(test)-1)
+	fmt.Println(test[len(test)/2], "======")
+	test = []int{2, 2, 1, 1, 1, 2, 2}
+	quick_sort(test, 0, len(test)-1)
+	fmt.Println(majorityElement(test), "======")
+}
diff --git a/Week_04/id_40/LeetCode_455_040.go b/Week_04/id_40/LeetCode_455_040.go
new file mode 100644
index 00000000..658325b6
--- /dev/null
+++ b/Week_04/id_40/LeetCode_455_040.go
@@ -0,0 +1,28 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+)
+
+func findContentChildren(g []int, s []int) int {
+	sort.Ints(g)
+	sort.Ints(s)
+	child := 0
+	cookie := 0
+	for child < len(g) && cookie < len(s) {
+		if g[child] <= s[cookie] {
+			child++
+		}
+		cookie++
+	}
+	return child
+}
+func main() {
+	child := []int{1, 2, 3}
+	cookie := []int{1, 1}
+	fmt.Println(findContentChildren(child, cookie), "______")
+	child = []int{1, 2}
+	cookie = []int{1, 2, 3}
+	fmt.Println(findContentChildren(child, cookie), "______")
+}