Commit 3464565

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Merge pull request #15 from mihirs16/master

added leetcode questions

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	`1`	`+# minimum absolute difference in BST \| leetcode 530 \| https://leetcode.com/problems/minimum-absolute-difference-in-bst/`
	`2`	`+# method: dfs, inorder traversal`
	`3`	`+`
	`4`	`+# Definition for a binary tree node.`
	`5`	`+class TreeNode:`
	`6`	`+ def __init__(self, val=0, left=None, right=None):`
	`7`	`+ self.val = val`
	`8`	`+ self.left = left`
	`9`	`+ self.right = right`
	`10`	`+`
	`11`	`+class Solution:`
	`12`	`+ def getMinimumDifference(self, root: TreeNode):`
	`13`	`+ minDiff = float('inf')`
	`14`	`+ prevNod = None`
	`15`	`+`
	`16`	`+ def dfs(node):`
	`17`	`+ nonlocal minDiff, prevNod`
	`18`	`+ if node is None:`
	`19`	`+ return`
	`20`	`+`
	`21`	`+ dfs(node.left)`
	`22`	`+`
	`23`	`+ if prevNod != None:`
	`24`	`+ minDiff = min(minDiff, abs(node.val - prevNod))`
	`25`	`+ prevNod = node.val`
	`26`	`+`
	`27`	`+ dfs(node.right)`
	`28`	`+`
	`29`	`+ dfs(root)`
	`30`	`+ return minDiff`
	`31`	`+`
	`32`	`+`

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	`1`	`+# all paths from source to target \| leetcode 797 \| https://leetcode.com/problems/all-paths-from-source-to-target/`
	`2`	`+# method: dfs`
	`3`	`+`
	`4`	`+class Solution:`
	`5`	`+ def allPathsSourceTarget(self, graph: list[list[int]]) -> list[list[int]]:`
	`6`	`+ possiblePaths = []`
	`7`	`+`
	`8`	`+ def dfs(node, visited):`
	`9`	`+ if node == len(graph) - 1:`
	`10`	`+ possiblePaths.append(visited)`
	`11`	`+`
	`12`	`+ for neighbour in graph[node]:`
	`13`	`+ dfs(neighbour, [*visited, node])`
	`14`	`+`
	`15`	`+ dfs(0, [0])`
	`16`	`+ return possiblePaths`

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	`1`	`+# unique binary search trees \| leetcode 96 \| https://leetcode.com/problems/unique-binary-search-trees/`
	`2`	`+# method: dp, use cached results for subtrees of all possible roots`
	`3`	`+`
	`4`	`+class Solution:`
	`5`	`+ def numTrees(self, n: int) -> int:`
	`6`	`+ # cache of possible trees`
	`7`	`+ possibleTrees = [1] * (n + 1)`
	`8`	`+`
	`9`	`+ # for each number of nodes`
	`10`	`+ for numNodes in range(2, n + 1):`
	`11`	`+`
	`12`	`+ # for each possible root`
	`13`	`+ possibleSubTrees = 0`
	`14`	`+ for possibleRoot in range(1, numNodes + 1):`
	`15`	`+ Left = possibleRoot - 1`
	`16`	`+ Right = numNodes - possibleRoot`
	`17`	`+ possibleSubTrees += possibleTrees[Left] * possibleTrees[Right]`
	`18`	`+ possibleTrees[numNodes] = possibleSubTrees`
	`19`	`+`
	`20`	`+ return possibleTrees[n]`
	`21`	`+`

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	`1`	`+# find the town judge \| leetcode 997 \| https://leetcode.com/problems/find-the-town-judge/submissions/`
	`2`	`+# method: decrement trust value if you trust someone, increment if someone trusts you`
	`3`	`+`
	`4`	`+class Solution:`
	`5`	`+ def findJudge(self, n: int, trust: list[list[int]]) -> int:`
	`6`	`+`
	`7`	`+ # for each person`
	`8`	`+ # trust += 1 if someone trusts you`
	`9`	`+ # trust -= 1 if you trust someone`
	`10`	`+ trustValue = [0] * (n + 1)`
	`11`	`+`
	`12`	`+ for edge in trust:`
	`13`	`+ trustValue[edge[0]] -= 1`
	`14`	`+ trustValue[edge[1]] += 1`
	`15`	`+`
	`16`	`+ for i in range(1, n + 1):`
	`17`	`+ if trustValue[i] == (n - 1):`
	`18`	`+ return i`
	`19`	`+`
	`20`	`+ return -1`
	`21`	`+`

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