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Commit 2251ab9

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Merge pull request doocs#240 from phuclhv/master
Add Python Solution to 559,774 and 743
2 parents baafff8 + 04e79ff commit 2251ab9

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"""
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# Definition for a Node.
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class Node:
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def __init__(self, val=None, children=None):
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self.val = val
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self.children = children
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"""
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# Performance
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'''
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Runtime: 36 ms, faster than 99.57% of Python3 online submissions for Maximum Depth of N-ary Tree.
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Memory Usage: 14.5 MB, less than 100.00% of Python3 online submissions for Maximum Depth of N-ary Tree.
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'''
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class Solution:
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def maxDepth(self, root: 'Node') -> int:
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if not root:
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return 0
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max_depth = 1
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for child in root.children:
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max_depth = max(self.maxDepth(child) + 1 , max_depth)
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#print(max_depth, root.val)
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return max_depth
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'''
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Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1.
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'''
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# Perfomance
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'''
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Runtime: 268 ms, faster than 84.25% of Python3 online submissions for Binary Search.
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Memory Usage: 14 MB, less than 100.00% of Python3 online submissions for Binary Search.
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'''
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class Solution:
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def search(self, nums: List[int], target: int) -> int:
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low, high = 0, len(nums) - 1
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while low <= high:
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mid = low + (high - low) // 2
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if nums[mid] == target:
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return mid
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elif nums[mid] < target:
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low = mid + 1
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else:
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high = mid - 1
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return -1
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'''
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There are N network nodes, labelled 1 to N.
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Given times, a list of travel times as directed edges times[i] = (u, v, w), where u is the source node, v is the target node, and w is the time it takes for a signal to travel from source to target.
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Now, we send a signal from a certain node K. How long will it take for all nodes to receive the signal? If it is impossible, return -1.
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'''
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# Performance
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'''
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Runtime: 496 ms, faster than 91.63% of Python3 online submissions for Network Delay Time.
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Memory Usage: 14.7 MB, less than 46.15% of Python3 online submissions for Network Delay Time.
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'''
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from collections import deque
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class Solution:
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def networkDelayTime(self, times: List[List[int]], N: int, K: int) -> int:
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# Build N+1 because index is from 1-N
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travel_times = [[] for y in range(N+1)]
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# Build the array of travel times to reduce cost of searching later
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for time in times:
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origin, dest, time_travel = time
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travel_times[origin].append((dest, time_travel))
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# Store the shortest amount of time to reach i-th node
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visited_times = [float('inf') for x in range(N+1)]
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visited_times[0] = 0
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visited_times[K] = 0
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# Store next traverse in line
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visited_queue = deque()
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visited_queue.append(K)
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# BFS
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while visited_queue:
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cur_node = visited_queue.popleft()
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for time in travel_times[cur_node]:
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(dest, time_travel) = time
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if time_travel + visited_times[cur_node] < visited_times[dest]:
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visited_times[dest] = time_travel + visited_times[cur_node]
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visited_queue.append(dest)
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# Only return the max if all were traversed. Return -1 otherwise
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return max(visited_times) if max(visited_times) != float('inf') else -1

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