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Commit3cad8d8

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1 parent6cf16d4 commit3cad8d8

6 files changed

+220
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lines changed

‎104. Maximum Depth of Binary Tree.go‎

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,5 +14,11 @@ func maxDepth(root *TreeNode) int {
1414
}
1515
l:=maxDepth(root.Left)
1616
r:=maxDepth(root.Right)
17-
returnint(math.Max(float64(l),float64(r)))+1
17+
returnmax(l,r)+1
18+
}
19+
funcmax(x,yint)int {
20+
ifx>y {
21+
returnx
22+
}
23+
returny
1824
}
Lines changed: 54 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,54 @@
1+
package main
2+
3+
typeTreeNodestruct {
4+
Valint
5+
Left*TreeNode
6+
Right*TreeNode
7+
}
8+
9+
/**
10+
根据中序和后续遍历结果，重建二叉树
11+
后续遍历的最后一个元素，是二叉树的root节点
12+
到中序数组中，root节点的位置，则左边用来递归创建左子树，右边用来递归创建右子树
13+
*/
14+
15+
typeIndexstruct {
16+
indexint
17+
}
18+
19+
funcbuildTree(inorder []int,postorder []int)*TreeNode {
20+
iflen(inorder)==0 {
21+
returnnil
22+
}
23+
//后续遍历的最后一个元素，是二叉树的root节点
24+
rootIndex:=&Index{len(postorder)-1}
25+
returnbuildTreeR(inorder,postorder,0,len(postorder)-1,rootIndex)
26+
}
27+
28+
funcbuildTreeR(inorder []int,postorder []int,startint,endint,rootIndex*Index)*TreeNode {
29+
ifstart>end {
30+
returnnil
31+
}
32+
33+
rootValue:=postorder[rootIndex.index]
34+
root:=&TreeNode{rootValue,nil,nil}
35+
rootIndex.index--
36+
37+
ifstart==end {
38+
returnroot
39+
}
40+
41+
//找到中序数组中，root节点的位置，则左边用来递归创建左子树，右边用来递归创建右子树
42+
index:=0
43+
fori:=start;i<=end;i++ {
44+
ifinorder[i]==rootValue {
45+
index=i
46+
break
47+
}
48+
}
49+
50+
root.Right=buildTreeR(inorder,postorder,index+1,end,rootIndex)
51+
root.Left=buildTreeR(inorder,postorder,start,index-1,rootIndex)
52+
53+
returnroot
54+
}

‎120. Triangle.go‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,36 @@
1+
package main
2+
3+
/**
4+
dp算法
5+
dp数组保存当前行获得的最小值
6+
从下往上转移
7+
初始化为最后一行的值
8+
*/
9+
10+
funcminimumTotal(triangle [][]int)int {
11+
l:=len(triangle)
12+
ifl==0 {
13+
return0
14+
}
15+
ifl==1 {
16+
returntriangle[0][0]
17+
}
18+
dp:=make([]int,l)
19+
//dp数组初始化成最后一行的值
20+
fori:=0;i<l;i++ {
21+
dp[i]=triangle[l-1][i]
22+
}
23+
fori:=l-2;i>=0;i-- {
24+
forj:=0;j<len(triangle[i]);j++ {
25+
dp[j]=min(dp[j],dp[j+1])+triangle[i][j]
26+
}
27+
}
28+
returndp[0]
29+
}
30+
funcmin(x,yint)int {
31+
ifx>y {
32+
returny
33+
}
34+
returnx
35+
36+
}

‎18. 4Sum.go‎

Lines changed: 51 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,51 @@
1+
package main
2+
3+
import (
4+
"sort"
5+
)
6+
7+
/**
8+
四重循环加上剪枝AC
9+
三重循环加上左右指针居然MLE
10+
晕。。。
11+
*/
12+
funcfourSum(nums []int,targetint) [][]int {
13+
varret [][]int
14+
sort.Ints(nums)
15+
val:= [...]int{0,0,0}
16+
fori:=0;i<len(nums);i++ {
17+
ifi>0&&nums[i-1]==nums[i] {
18+
continue
19+
}
20+
forj:=i+1;j<len(nums);j++ {
21+
val[0]=nums[i]+nums[j]
22+
ifval[0]>target&&nums[j]>0 {//后面不可能有解
23+
break
24+
}
25+
ifj>i+1&&nums[j-1]==nums[j] {//相同元素
26+
continue
27+
}
28+
fork:=j+1;k<len(nums);k++ {
29+
val[1]=val[0]+nums[k]
30+
ifval[1]>target&&nums[k]>0 {
31+
break
32+
}
33+
ifk>j+1&&nums[k-1]==nums[k] {
34+
continue
35+
}
36+
form:=k+1;m<len(nums);m++ {
37+
val[2]=val[1]+nums[m]
38+
ifval[2]==target {
39+
tmp:= []int{nums[i],nums[j],nums[k],nums[m]}
40+
ret=append(ret,tmp)
41+
break
42+
}
43+
ifval[2]>target {
44+
break
45+
}
46+
}
47+
}
48+
}
49+
}
50+
returnret
51+
}

‎23. Merge k Sorted Lists.go‎

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,43 @@
1+
package main
2+
3+
typeListNodestruct {
4+
Valint
5+
Next*ListNode
6+
}
7+
8+
/**
9+
分治的方法，不停的两两merge
10+
其中merge两个list的方法，就是#21
11+
*/
12+
13+
funcmergeKLists(lists []*ListNode)*ListNode {
14+
iflen(lists)==0 {
15+
returnnil
16+
}
17+
begin,end:=0,len(lists)-1
18+
forbegin<end {
19+
mid:= (begin+end-1)/2
20+
fori:=0;i<=mid;i++ {
21+
lists[i]=mergeTwoLists(lists[i],lists[end-i])
22+
}
23+
end= (begin+end)/2
24+
}
25+
returnlists[0]
26+
}
27+
28+
funcmergeTwoLists(l1*ListNode,l2*ListNode)*ListNode {
29+
ifl1==nil {
30+
returnl2
31+
}
32+
ifl2==nil {
33+
returnl1
34+
}
35+
ifl1.Val<l2.Val {
36+
l1.Next=mergeTwoLists(l1.Next,l2)
37+
returnl1
38+
}else {
39+
l2.Next=mergeTwoLists(l1,l2.Next)
40+
returnl2
41+
}
42+
43+
}

‎92. Reverse Linked List II.go‎

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
1+
package main
2+
3+
typeListNodestruct {
4+
Valint
5+
Next*ListNode
6+
}
7+
8+
funcreverseBetween(head*ListNode,mint,nint)*ListNode {
9+
shadowHead:=&ListNode{Next:head}//用于返回
10+
prevNode:=shadowHead
11+
//走到反转的起点位置
12+
fori:=1;i<m;i++ {
13+
prevNode=prevNode.Next
14+
head=head.Next
15+
}
16+
mNode:=head
17+
nNode:=head.Next
18+
//开始反转操作
19+
fori:=m;i<n;i++ {
20+
nextNNode:=nNode.Next
21+
nNode.Next=head
22+
head=nNode
23+
nNode=nextNNode
24+
}
25+
//把反转之后的list和原来的对接
26+
mNode.Next=nNode
27+
prevNode.Next=head
28+
returnshadowHead.Next
29+
}

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