Add offer100

Author: beyondyyh

algorithms/README.md

@@ -68,4 +68,7 @@
 |1108|[地址无效化](https://leetcode-cn.com/problems/defanging-an-ip-address/)|[go](./mystring/1108.defangIPaddr.go)|S|
 |1213|[三个有序数组的交集](https://leetcode-cn.com/problems/intersection-of-three-sorted-arrays/)|[go](./myarray/1213.arraysIntersection.go)|S|
 |1367|[二叉树中的列表](https://leetcode-cn.com/problems/linked-list-in-binary-tree/)|[go](./tree/1367.isSubPath.go)|M|
+|-|-|-|-|
+|58|[左旋转字符串](https://leetcode-cn.com/problems/zuo-xuan-zhuan-zi-fu-chuan-lcof/)|[go](./offer100/58.reverseLeftWords.go)|S|
+|22|[链表中倒数第k个节点](https://leetcode-cn.com/problems/lian-biao-zhong-dao-shu-di-kge-jie-dian-lcof/)|[go](./offer100/22.getKthFromEnd.go)|S
 ||||[:top:](#Top)|

algorithms/offer100/22.getKthFromEnd.go

@@ -0,0 +1,33 @@
+package offer100
+
+import "fmt"
+
+// 由于链表只能从Head开始遍历，如果要计算链表长度则需要遍历一次，
+// 为减少时间复杂度，可以使用快慢指针法
+func getKthFromEnd(head *ListNode, k int) *ListNode {
+	if head == nil {
+		return nil
+	}
+
+	slow, fast := head, head
+
+	// 快指针先移动k步，fast != nil是为了处理当 n > len(链表) 越界情况
+	for k != 0 && fast != nil {
+		fast = fast.Next
+		k--
+	}
+
+	// if n >= len(链表)，返回头结点
+	if fast == nil {
+		return head
+	}
+	fmt.Println(fast.Val)
+
+	// 快慢指针同时开始移动
+	for fast != nil {
+		fast = fast.Next
+		slow = slow.Next
+	}
+
+	return slow
+}

algorithms/offer100/22.getKthFromEnd_test.go

@@ -0,0 +1,40 @@
+package offer100
+
+import (
+	"Leetcode/algorithms/kit"
+	"reflect"
+	"testing"
+)
+
+// run: go test -run Test_getKthFromEnd
+func Test_getKthFromEnd(t *testing.T) {
+	cases := []CaseEntry{
+		{
+			Name: "x1",
+			Input: []interface{}{
+				[]int{1, 2, 3, 4, 5}, 2,
+			},
+			Expected: []int{4, 5},
+		},
+		{
+			Name: "x1",
+			Input: []interface{}{
+				[]int{1, 2, 3, 4, 5}, 4,
+			},
+			Expected: []int{1, 2, 3, 4, 5},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.Name, func(t *testing.T) {
+			head := kit.Ints2List(c.Input.([]interface{})[0].([]int))
+			k := c.Input.([]interface{})[1].(int)
+
+			out2Ints := kit.List2Ints(getKthFromEnd(head, k))
+			exp2Ints := c.Expected.([]int)
+			if !reflect.DeepEqual(out2Ints, exp2Ints) {
+				t.Errorf("getKthFromEnd(%v, %d)=%v, expected=%v", c.Input.([]interface{})[0].([]int), k, out2Ints, exp2Ints)
+			}
+		})
+	}
+}

algorithms/offer100/58.reverseLeftWords.go

@@ -0,0 +1,15 @@
+package offer100
+
+// 利用字符串切片
+func reverseLeftWords1(s string, n int) string {
+	return s[n:] + s[:n]
+}
+
+// 遍历，巧妙利用mod
+func reverseLeftWords2(s string, n int) string {
+	var ans string
+	for i := n; i < len(s)+n; i++ {
+		ans += string(s[i%len(s)])
+	}
+	return ans
+}

algorithms/offer100/58.reverseLeftWords_test.go

@@ -0,0 +1,39 @@
+package offer100
+
+import (
+	"testing"
+)
+
+// run: go test -run Test_reverseLeftWords
+func Test_reverseLeftWords(t *testing.T) {
+	cases := []CaseEntry{
+		{
+			Name: "x1",
+			Input: []interface{}{
+				"abcdefg", 2,
+			},
+			Expected: "cdefgab",
+		},
+		{
+			Name: "x2",
+			Input: []interface{}{
+				"lrloseumgh", 6,
+			},
+			Expected: "umghlrlose",
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.Name, func(t *testing.T) {
+			s := c.Input.([]interface{})[0].(string)
+			k := c.Input.([]interface{})[1].(int)
+			if output := reverseLeftWords1(s, k); output != c.Expected.(string) {
+				t.Errorf("reverseLeftWords1(%s, %d)=%s, expected=%s", s, k, output, c.Expected.(string))
+			}
+
+			if output := reverseLeftWords2(s, k); output != c.Expected.(string) {
+				t.Errorf("reverseLeftWords2(%s, %d)=%s, expected=%s", s, k, output, c.Expected.(string))
+			}
+		})
+	}
+}

algorithms/offer100/base.go

@@ -0,0 +1,9 @@
+package offer100
+
+import (
+	"Leetcode/algorithms/kit"
+)
+
+type CaseEntry = kit.CaseEntry
+type ListNode = kit.ListNode
+type DListNode = kit.DListNode