practice

Author: limingzhong

TODO.md

@@ -6,3 +6,5 @@
 - [ ] 工程实现用到的算法解析
 - [ ] 周赛计划
 - [ ] 面试体系计划
+
+https://www.ctolib.com/0xAX-go-algorithms.html

src/linkedlist/list.go

@@ -0,0 +1,98 @@
+package linkedlist
+
+import "fmt"
+
+type ListNode struct {
+	val  interface{}
+	pre  *ListNode
+	next *ListNode
+}
+
+func NewIntList(nums []int) *ListNode {
+	if len(nums) == 0 {
+		return nil
+	}
+	dummy := &ListNode{}
+	head := dummy
+	for _, val := range nums {
+		node := &ListNode{
+			val: val,
+		}
+		node.pre = head
+		head.next = node
+		head = node
+	}
+
+	return dummy.next
+}
+
+func (head *ListNode) Print() {
+	curr := head
+	for curr != nil {
+		fmt.Printf("%v, ", curr.val)
+		curr = curr.next
+	}
+	println()
+}
+
+func (head *ListNode) String() string {
+	s := ""
+	curr := head
+	for curr != nil {
+		s += fmt.Sprintf("%v, ", curr.val)
+		curr = curr.next
+	}
+	return s
+}
+
+// 给定一个排序链表，删除所有重复的元素，使得每个元素只出现一次。
+func DeleteDuplicates(head *ListNode) *ListNode {
+	current := head
+	for current != nil {
+		for current.next != nil && current.next.val == current.val {
+			current.next = current.next.next
+		}
+		current = current.next
+	}
+
+	return head
+}
+
+// 给定一个排序链表，删除所有含有重复数字的节点，只保留原始链表中   没有重复出现的数字。
+// 只出现一次的节点
+func DeleteDupKeepOnce(head *ListNode) *ListNode {
+	dummy := &ListNode{}
+	dummy.next = head
+	current := dummy
+
+	var rmVal interface{}
+	for current.next != nil && current.next.next != nil {
+		if current.next.val == current.next.next.val {
+			rmVal = current.next.val
+			// 指针直接跳到第三个节点
+			current.next = current.next.next.next
+			// 顺序删除
+			for current.next != nil && current.next.val == rmVal {
+				current.next = current.next.next
+			}
+		} else {
+			current = current.next
+		}
+	}
+
+	return dummy.next
+}
+
+// 反转一个单链表。
+// 思路：用一个 prev 节点保存向前指针，temp 保存向后的临时指针
+func ReverseList(head *ListNode) *ListNode {
+	var pre *ListNode
+	for head != nil {
+		temp := head.next
+		head.next = pre
+		pre = head
+		head = temp
+	}
+
+	return pre
+}

src/linkedlist/list_test.go

@@ -0,0 +1,33 @@
+package linkedlist
+
+import "testing"
+
+func defaultSortedList() *ListNode {
+	return NewIntList([]int{1, 2, 2, 2, 2, 3, 3, 4, 5, 5})
+}
+
+func TestNewIntList(t *testing.T) {
+	list := defaultSortedList()
+	list.Print()
+	println(list.String())
+}
+
+func TestDeleteDuplicates(t *testing.T) {
+	head := defaultSortedList()
+	head.Print()
+	DeleteDuplicates(head)
+	head.Print()
+}
+
+func TestDeleteDupKeepOnce(t *testing.T) {
+	head := defaultSortedList()
+	head.Print()
+	DeleteDupKeepOnce(head)
+	head.Print()
+}
+
+func TestReverseList(t *testing.T) {
+	head := defaultSortedList()
+	head.Print()
+	ReverseList(head).Print()
+}

src/str/str.go

@@ -0,0 +1,20 @@
+package str
+
+// O(m*n)
+func Contain(haystack string, needle string) int {
+	if len(needle) == 0 {
+		return 0
+	}
+	var i, j int
+	for i = 0; i < len(haystack)-len(needle)+1; i++ {
+		for ; j < len(needle); j++ {
+			if haystack[i+j] != needle[j] {
+				break
+			}
+		}
+		if j == len(needle) {
+			return i
+		}
+	}
+	return -1
+}

src/str/str_test.go

@@ -0,0 +1,9 @@
+package str
+
+import "testing"
+
+func TestContain(t *testing.T) {
+	str := "abcdeqqqqqwww"
+	needle := "www"
+	println(Contain(str, needle))
+}