algorithm001
diff --git a/Week_02/id_103/.idea/workspace.xml b/Week_02/id_103/.idea/workspace.xml
diff --git a/Week_04/id_103/.gitignore b/Week_04/id_103/.gitignore
@@ -0,0 +1,14 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, build with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+.idea
diff --git a/Week_04/id_103/NOTE.md b/Week_04/id_103/NOTE.md
@@ -1 +1,5 @@
-# 学习笔记
+# 学习笔记
+
+- 169 既然一个数半数都存在，那排好序之后，一定在中间
+- 455 这个排序后，看每块饼干能否满足小朋友，能的话，就递增，不能就再继续，就能判断出来了，不过对小朋友的胃口和饼干要提前排序。
+- 746 到达当前台阶时判断下从前一个台阶过来省事，还是从前一个的前一个过来省事，一直累加到最后一个台阶完，最小值就是最省体力的。 用p1和p2表示前两个和前一个台阶所耗费的体力，一遍循环就可以了。
diff --git a/Week_04/id_103/leetcode_103_169.go b/Week_04/id_103/leetcode_103_169.go
@@ -0,0 +1,8 @@
+package id_103
+
+import "sort"
+
+func majorityElement(nums []int) int {
+	sort.Ints(nums)
+	return nums[len(nums) / 2]
+}
diff --git a/Week_04/id_103/leetcode_103_455.go b/Week_04/id_103/leetcode_103_455.go
@@ -0,0 +1,16 @@
+package id_103
+
+import "sort"
+
+func findContentChildren(g []int, s []int) int {
+	sort.Ints(g)
+	sort.Ints(s)
+	child, cookie := 0,0
+	for child < len(g) && cookie < len(s){
+		if g[child] <= s[cookie]{
+			child++
+		}
+		cookie++
+	}
+	return child
+}
diff --git a/Week_04/id_103/leetcode_103_746.go b/Week_04/id_103/leetcode_103_746.go
@@ -0,0 +1,17 @@
+package id_103
+
+func minCostClimbingStairs(cost []int) int {
+	p1,p2 := 0,0
+	for i := 2; i <= len(cost); i++ {
+		p1 , p2 = p2, min(p2 + cost[i-1],p1+cost[i-2])
+	}
+	return p2
+}
+
+func min(a,b int) int  {
+	if a > b{
+		return b
+	}else{
+		return a
+	}
+}