Commit 281d855

committed

Merge pull request #372 from 0xff-dev/124

Add solution and test-cases for problem 124

2 parents de8b9f4 + 0d777d5 commit 281d855Copy full SHA for 281d855

File tree

+85

-0

lines changed

+85

-0

lines changed

Lines changed: 33 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,33 @@`
	`1`	`+# [124.Binary Tree Maximum Path Sum][title]`
	`2`	`+`
	`3`	`+## Description`
	`4`	`+A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence at most once. Note that the path does not need to pass through the root.`
	`5`	`+`
	`6`	`+The path sum of a path is the sum of the node's values in the path.`
	`7`	`+`
	`8`	+Given the `root` of a binary tree, return the maximum path sum of any non-empty path.
	`9`	`+`
	`10`	`+Example 1:`
	`11`	`+![example1](./exx1.jpg)`
	`12`	`+`
	`13`	+```
	`14`	`+Input: root = [1,2,3]`
	`15`	`+Output: 6`
	`16`	`+Explanation: The optimal path is 2 -> 1 -> 3 with a path sum of 2 + 1 + 3 = 6.`
	`17`	+```
	`18`	`+`
	`19`	`+Example 2:`
	`20`	`+![example2](./exx2.jpg)`
	`21`	`+`
	`22`	+```
	`23`	`+Input: root = [-10,9,20,null,null,15,7]`
	`24`	`+Output: 42`
	`25`	`+Explanation: The optimal path is 15 -> 20 -> 7 with a path sum of 15 + 20 + 7 = 42.`
	`26`	+```
	`27`	`+`
	`28`	`+## 结语`
	`29`	`+`
	`30`	`+如果你同我一样热爱数据结构、算法、LeetCode,可以关注我 GitHub 上的 LeetCode 题解:[awesome-golang-algorithm][me]`
	`31`	`+`
	`32`	`+[title]: https://leetcode.com/problems/binary-tree-maximum-path-sum`
	`33`	`+[me]: https://github.com/kylesliu/awesome-golang-algorithm`

Lines changed: 51 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -29,3 +29,54 @@ func max(x, y int) int {`
`29`	`29`	`}`
`30`	`30`	`return y`
`31`	`31`	`}`
	`32`	`+`
	`33`	`+func maxPathSum_2(root *TreeNode) int {`
	`34`	`+ ans := 0`
	`35`	`+ ansInit := false`
	`36`	`+ maxPathSum124(root, &ans, &ansInit)`
	`37`	`+ return ans`
	`38`	`+}`
	`39`	`+func maxPathSum124(root TreeNode, ans int, ansInit *bool) (int, int) {`
	`40`	`+ if root == nil {`
	`41`	`+ return 0, 0`
	`42`	`+ }`
	`43`	`+`
	`44`	`+ ll, lr := maxPathSum124(root.Left, ans, ansInit)`
	`45`	`+ rl, rr := maxPathSum124(root.Right, ans, ansInit)`
	`46`	`+ lmax := ll`
	`47`	`+ if lr > lmax {`
	`48`	`+ lmax = lr`
	`49`	`+ }`
	`50`	`+`
	`51`	`+ rmax := rr`
	`52`	`+ if rl > rmax {`
	`53`	`+ rmax = rl`
	`54`	`+ }`
	`55`	`+`
	`56`	`+ returnL, returnR := root.Val, root.Val`
	`57`	`+ l := lmax + root.Val`
	`58`	`+ r := rmax + root.Val`
	`59`	`+ if !ansInit \|\| l > ans {`
	`60`	`+ *ans = l`
	`61`	`+ *ansInit = true`
	`62`	`+ }`
	`63`	`+ if !ansInit \|\| r > ans {`
	`64`	`+ *ans = r`
	`65`	`+ *ansInit = true`
	`66`	`+ }`
	`67`	`+ if r := l + rmax; !ansInit \|\| r > ans {`
	`68`	`+ *ans = r`
	`69`	`+ *ansInit = true`
	`70`	`+ }`
	`71`	`+ if !ansInit \|\| root.Val > ans {`
	`72`	`+ *ans = root.Val`
	`73`	`+ *ansInit = true`
	`74`	`+ }`
	`75`	`+ if l > root.Val {`
	`76`	`+ returnL = l`
	`77`	`+ }`
	`78`	`+ if r > root.Val {`
	`79`	`+ returnR = r`
	`80`	`+ }`
	`81`	`+ return returnL, returnR`
	`82`	`+}`

Lines changed: 1 addition & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -15,6 +15,7 @@ type SolutionFuncType func(node *TreeNode) int`
`15`	`15`
`16`	`16`	`var SolutionFuncList = []SolutionFuncType{`
`17`	`17`	`maxPathSum_1,`
	`18`	`+ maxPathSum_2,`
`18`	`19`	`}`
`19`	`20`
`20`	`21`	`// Test case info struct`

6.83 KB

12.8 KB

Comments

(0)