第四周作业_006

.gitignore

@@ -1 +1,2 @@
 .DS_Store
+.idea

Week_04/id_6/LeetCode_053_6.go

@@ -0,0 +1,33 @@
+package main
+
+import "fmt"
+
+/**
+时间复杂度：O(n)
+空间复杂度：O(1)
+ */
+func maxSubArray(nums []int) int {
+	answer := nums[0]
+	sum := 0
+	for _, v := range nums{
+		if sum > 0 {
+			sum += v
+		}else {
+			// 如果 sum 小于 0 那还不如从当前位置开始计算
+			sum = v
+		}
+		answer = maxInt(sum, answer)
+	}
+	return answer
+}
+
+func maxInt(a int, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+func main()  {
+	fmt.Println("结果是：", maxSubArray([]int{-2,1,-3,4,-1,2,1,-5,4}))
+}

Week_04/id_6/LeetCode_169_6.go

@@ -0,0 +1,80 @@
+package main
+
+import "fmt"
+
+/**
+暴力法
+时间复杂度：O(n^2)
+空间复杂度：O(1)
+ */
+func majorityElement(nums []int) int {
+	majorityCount := len(nums)/2
+	for _, v := range nums {
+		count := 0
+		for _, num := range nums {
+			if v == num {
+				count++
+			}
+		}
+		if count > majorityCount {
+			return v
+		}
+	}
+	return -1
+}
+
+/**
+哈希表
+时间复杂度：O(n)
+空间复杂度：O(n)
+ */
+func majorityElement1(nums []int) int {
+	majorityCount := len(nums)/2
+	m := make(map[int]int, len(nums))
+	for _, num := range nums {
+		if _, ok := m[num]; ok {
+			m[num]++
+		}else {
+			m[num] = 1
+		}
+	}
+	for k := range m {
+		if m[k] > majorityCount {
+			return k
+		}
+	}
+	return -1
+}
+
+/**
+Boyer-Moore 投票算法 (当不存在众数的时候此方法不适合)
+时间复杂度：O(n)
+空间复杂度：O(1)
+*/
+func majorityElement2(nums []int) int {
+	count := 0
+	var candidate int
+
+	for _, num := range nums {
+		if count == 0 {
+			candidate = num
+		}
+		if num == candidate {
+			count += 1
+		}else {
+			count -= 1
+		}
+	}
+	return candidate
+}
+
+func main()  {
+	nums := []int{3,2,3}
+	fmt.Println("结果是：", majorityElement(nums))
+
+	nums1 := []int{3,2,3}
+	fmt.Println("结果是：", majorityElement1(nums1))
+
+	nums2 := []int{3,2,3}
+	fmt.Println("结果是：", majorityElement2(nums2))
+}