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437.py
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437.py
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__________________________________________________________________________________________________
sample 44 ms submission
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
from collections import defaultdict
'''
class Solution:
def has_sum(self, sum_, path): # [10, 5, 2, 1] = [18, 8, 3, 1]
tmp_path = [0] * len(path)
count = 0
for i in range(len(path)-1, -1, -1):
if i< len(path)-1:
tmp_path[i] += path[i]+tmp_path[i+1]
else:
tmp_path[i] = path[i]
if tmp_path[i] ==sum_:
count +=1
return count
def helper(self, node, sum_, path):
if node is None:
return
path.append(node.val)
self.result += self.has_sum(sum_, path)
self.helper(node.left, sum_, path)
self.helper(node.right, sum_, path)
path.pop()
return
def pathSum(self, root, sum_):
"""
:type root: TreeNode
:type sum: int
:rtype: int
"""
path=[]
self.result = 0;
self.helper(root, sum_, path)
return self.result
'''
'''
class Solution:
def subarraySum(self, nums, k):
"""
:type nums: List[int]
:type k: int
:rtype: int
"""
result = 0
prefix_sum = 0
hash_map ={} # set up a dictionary, and initialize with a key-value pair of 0, 1
hash_map[0]=1
for i in range(len(nums)):
prefix_sum += nums[i]
if prefix_sum-k in hash_map:
result += hash_map[prefix_sum -k]
hash_map[prefix_sum]=1 if prefix_sum not in hash_map else hash_map[prefix_sum]+1 # one line
return result
def helper(self, node, sum_, path):
if node is None:
return
path.append(node.val)
if self.subarraySum(path,sum_)>0:
print(path)
self.result += self.subarraySum(path, sum_)
self.helper(node.left, sum_, path)
self.helper(node.right, sum_, path)
path.pop()
return
def pathSum(self, root, sum_):
"""
:type root: TreeNode
:type sum: int
:rtype: int
"""
path=[]
self.result = 0;
self.helper(root, sum_, path)
return self.result
# does not really work
# [10, 5, 3]
#[10, 5, 3, 3]
#[10, 5, 3, -2]
#[10, 5, 2, 1]
#[10, -3, 11]
# [-, 5, 3, -] is counted three times.
'''
class Solution1:
def helper(self, node, cur, sum_, lookup):
if node is None:
#print('None is reached')
return
cur +=node.val;
if cur - sum_ in lookup:
self.result += lookup[cur - sum_]
if cur in lookup:
lookup[cur]+=1
else:
lookup[cur]=1
#print('Before helpers, ', lookup)
#print('Call left')
self.helper(node.left, cur,sum_, lookup)
#print('Call right')
self.helper(node.right, cur, sum_, lookup)
#lookup[cur]-=1; # This step is very curcial. Not fully un
#print('After helpers,', lookup)
#if lookup[cur]==0:
# del lookup[cur]
#print('After Del,', lookup)
return
def pathSum(self, root, sum_):
"""
:type root: TreeNode
:type sum: int
:rtype: int
"""
lookup={}
lookup[0]=1
self.result = 0;
self.helper(root, 0, sum_, lookup)
return self.result
class Solution:
def pathSum(self, root, sum_):
lookup = defaultdict(int)
lookup[0] = 1
self.ans = 0
self.helper(root, 0, sum_, lookup)
return self.ans
def helper(self, node, pre_sum, sum_, lookup):
if not node:
return
pre_sum += node.val
if pre_sum - sum_ in lookup:
self.ans += lookup[pre_sum - sum_]
lookup [pre_sum] += 1
self.helper(node.left, pre_sum, sum_, lookup)
self.helper(node.right, pre_sum, sum_, lookup)
lookup[pre_sum] -= 1
return
__________________________________________________________________________________________________
sample 13364 kb submission
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def pathSum(self, root: TreeNode, goal: int) -> int:
if root is None:
return 0
stack=[(root,[root.val])]
num=0
while stack:
node,values=stack.pop()
num+=values.count(goal)
if node.left:
stack.append((node.left,[val+node.left.val for val in values]+[node.left.val]))
if node.right:
stack.append((node.right,[val+node.right.val for val in values]+[node.right.val]))
return num
__________________________________________________________________________________________________