add leetocde

19_RemoveNthNodeFromEndofList.py

@@ -0,0 +1,41 @@
+"""
+" File Description:
+" 
+"
+" Created by Rocha(chenzhihao) on 2020/12/17.
+" Mail: [email protected]
+"""
+
+
+# Definition for singly-linked list.
+class ListNode(object):
+	def __init__(self, val=0, next=None):
+		self.val = val
+		self.next = next
+
+
+class Solution(object):
+	def removeNthFromEnd(self, head, n):
+		"""
+		:type head: ListNode
+		:type n: int
+		:rtype: ListNode
+		"""
+		dummy_node = ListNode(0)
+		dummy_node.next = head
+
+		fast = dummy_node
+		slow = dummy_node
+
+
+		for i in range(n):
+			fast = fast.next
+
+		while fast.next:
+			fast = fast.next
+			slow = slow.next
+
+		slow.next = slow.next.next
+
+		return dummy_node.next
+

21_MergeTwoSortedLists.py

@@ -0,0 +1,33 @@
+"""
+" File Description:
+" Merge two sorted linked lists and return it as a new sorted list.
+The new list should be made by splicing together the nodes of the first two lists.
+"
+" Created by Rocha(chenzhihao) on 2020/12/17.
+" Mail: [email protected]
+"""
+
+
+# Definition for singly-linked list.
+class ListNode(object):
+	def __init__(self, val=0, next=None):
+		self.val = val
+		self.next = next
+
+
+class Solution(object):
+	def mergeTwoLists(self, l1, l2):
+		"""
+		:type l1: ListNode
+		:type l2: ListNode
+		:rtype: ListNode
+		"""
+		if not l1: return l2
+		if not l2: return l1
+
+		if l1.val > l2.val:
+			l2.next = self.mergeTwoLists(l1, l2.next)
+			return l2
+		else:
+			l1.next = self.mergeTwoLists(l1.next, l2)
+			return l1

34_FindFirstandLastPositionofElementinSortedArray.py

@@ -0,0 +1,21 @@
+"""
+" File Description:
+" Given an array of integers nums sorted in ascending order,
+find the starting and ending position of a given target value.
+
+If target is not found in the array, return [-1, -1].
+
+Follow up: Could you write an algorithm with O(log n) runtime complexity?
+"
+" Created by Rocha(chenzhihao) on 2020/12/17.
+" Mail: [email protected]
+"""
+
+
+class Solution(object):
+	def searchRange(self, nums, target):
+		"""
+		:type nums: List[int]
+		:type target: int
+		:rtype: List[int]
+		"""

39_Combination_Sum.py

@@ -0,0 +1,56 @@
+"""
+" File Description:
+" 
+"
+" Created by Rocha(chenzhihao) on 2020/6/26.
+"""
+
+
+class Solution(object):
+	def __getDp(self, candidates, sum):
+		if not self.dp[sum]:
+			self.dp[sum] = []
+			for i in candidates:
+				left = sum - i
+				if (left == 0):
+					self.dp[sum].append([i])
+					return self.dp[sum]
+
+				elif (left > 0):
+					ok = False
+					if not self.dp[left]:
+						self.__getDp(candidates, left)
+					if self.dp[left]:
+						ok = True
+
+					if(ok):
+						for comb in self.dp[left]:
+							tmp = comb.copy()
+							tmp.append(i)
+							tmp = sorted(tmp)
+							if tmp not in self.dp[sum]:
+								self.dp[sum].append(tmp)
+				else:
+					return None
+		else:
+			return self.dp[sum]
+
+
+	def combinationSum(self, candidates, target):
+		"""
+		:type candidates: List[int]
+		:type target: int
+		:rtype: List[List[int]]
+		"""
+		self.dp = [None] * (target+1)
+		candidates = sorted(candidates)
+
+		self.__getDp(candidates, target)
+
+		return self.dp[target]
+
+if __name__ == '__main__':
+	candidates = [2, 3, 5]
+	target = 8
+	so = Solution()
+	print(so.combinationSum(candidates, target))

39_Combination_Sum2.py

@@ -0,0 +1,37 @@
+class Solution(object):
+    def combinationSum2(self, candidates, target):
+        """
+        :type candidates: List[int]
+        :type target: int
+        :rtype: List[List[int]]
+        """
+        self.res = []
+        self.sorted_candidates = sorted(candidates)
+        self.len = len(self.sorted_candidates)
+        self.dfs(target, 0, [])
+
+        return self.res
+
+    def dfs(self,target, pos_start, vlist):
+        print("Search target: %s, Pos start: %s, vlist: %s" %(target, pos_start, vlist))
+        if target == 0:
+            self.res.append(vlist)
+            return
+        elif target < 0:
+            print("break")
+            return True
+        else:
+            for i in range(pos_start, self.len):
+                if(i > pos_start and self.sorted_candidates[i] == self.sorted_candidates[i-1]):
+                    continue     # remove duplicate
+
+                if_break = self.dfs(target-self.sorted_candidates[i], i+1, vlist + [self.sorted_candidates[i]])
+                if if_break:
+                    break
+
+
+if __name__ == '__main__':
+    candidates = [2,5,2,1,2]
+    target = 5
+    so = Solution()
+    print(so.combinationSum2(candidates, target))

7_reverse_integer.py

@@ -0,0 +1,47 @@
+"""
+" File Description:
+" Given a 32-bit signed integer, reverse digits of an integer.
+
+Note:
+Assume we are dealing with an environment that could only store integers within the 32-bit signed integer range:
+[−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
+
+
+"
+" Created by Rocha(chenzhihao) on 2020/12/15.
+" Mail: [email protected]
+"""
+
+import sys
+
+class Solution(object):
+	def reverse(self, x):
+		"""
+		:type x: int
+		:rtype: int
+		"""
+		res = 0
+		neg = False
+		maxint = 2**31 -1
+		minint = - 2**31
+
+		if x < 0:
+			neg = True
+			x = abs(x)
+
+		while x != 0:
+			res = (x % 10 + res * 10)
+			x //= 10
+
+			if not neg and res > maxint:
+				return 0
+			elif neg and res > abs(maxint):
+				return 0
+
+		if neg:
+			res = -res
+		return res
+
+if __name__ == '__main__':
+    so = Solution()
+    print(so.reverse(1534236469))