完成"Pattern: Sliding Window"的introduction部分

.gitignore

@@ -13,3 +13,7 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
+
+# idea file
+*.iml
+.idea

Pattern1 - Sliding Window/go.mod

@@ -0,0 +1,3 @@
+module pattern1
+
+go 1.13

Pattern1 - Sliding Window/introduction/brute-force.go

@@ -0,0 +1,15 @@
+package introduction
+
+func findAveragesOfSubArraysByBruteForce(K int, arr []int) []float64 {
+	results := make([]float64, len(arr)-K+1)
+	for i := 0; i <= len(arr)-K; i++ {
+		// 计算下一组K个元素的和
+		sum := 0
+		for j := i; j < i+K; j++ {
+			sum += arr[j]
+		}
+		// 计算平均
+		results[i] = float64(sum) / float64(K)
+	}
+	return results
+}

Pattern1 - Sliding Window/introduction/brute-fore_test.go

@@ -0,0 +1,23 @@
+package introduction
+
+import "testing"
+
+func TestFindAveragesOfSubArraysByBruteForce(t *testing.T) {
+	arr := []int{1, 3, 2, 6, -1, 4, 1, 8, 2}
+	results := findAveragesOfSubArraysByBruteForce(5, arr)
+	expected := []float64{2.2, 2.8, 2.4, 3.6, 2.8}
+	if len(results) != len(expected) {
+		t.Errorf("Averages of subarrays of size K(5): %d, answer is %f, expect is %f", arr, results, expected)
+	} else {
+		eq := true
+		for i := 0; i < len(results); i++ {
+			if results[i] != expected[i] {
+				eq = false
+				break
+			}
+		}
+		if !eq {
+			t.Errorf("Averages of subarrays of size K(5): %d, answer is %f, expect is %f", arr, results, expected)
+		}
+	}
+}

Pattern1 - Sliding Window/introduction/sliding-window.go

@@ -0,0 +1,20 @@
+package introduction
+
+func findAveragesOfSubArraysBySlidingWindow(K int, arr []int) []float64 {
+	results := make([]float64, len(arr)-K+1)
+	windowSum := 0
+	windowStart := 0
+	for windowEnd := 0; windowEnd < len(arr); windowEnd++ {
+		// 把下个元素加上
+		windowSum += arr[windowEnd]
+		// 滑动窗口，特别地，如果没有达到K个则不滑动
+		if windowEnd >= K-1 {
+			// 当前windowSum计算了整个窗口的和
+			results[windowStart] = float64(windowSum) / float64(K)
+			// 当前窗口计算完后，移动窗口需要先减去原来窗口头部的元素
+			windowSum -= arr[windowStart]
+			windowStart++
+		}
+	}
+	return results
+}

Pattern1 - Sliding Window/introduction/sliding-window_test.go

@@ -0,0 +1,23 @@
+package introduction
+
+import "testing"
+
+func TestFindAveragesOfSubArraysBySlidingWindow(t *testing.T) {
+	arr := []int{1, 3, 2, 6, -1, 4, 1, 8, 2}
+	results := findAveragesOfSubArraysBySlidingWindow(5, arr)
+	expected := []float64{2.2, 2.8, 2.4, 3.6, 2.8}
+	if len(results) != len(expected) {
+		t.Errorf("Averages of subarrays of size K(5): %d, answer is %f, expect is %f", arr, results, expected)
+	} else {
+		eq := true
+		for i := 0; i < len(results); i++ {
+			if results[i] != expected[i] {
+				eq = false
+				break
+			}
+		}
+		if !eq {
+			t.Errorf("Averages of subarrays of size K(5): %d, answer is %f, expect is %f", arr, results, expected)
+		}
+	}
+}