LeetCode Solution

Author: SamirPaulb

001_Two_Sum.py

@@ -0,0 +1,66 @@
+class Solution(object):
+    # def twoSum(self, nums, target):
+    #     """
+    #     :type nums: List[int]
+    #     :type target: int
+    #     :rtype: List[int]
+    #     """
+    #     #n^2
+    #     ls = len(nums)
+    #     for i in range(ls):
+    #         for j in range(i + 1, ls):
+    #             if nums[i] + nums[j] == target:
+    #                 return [i, j]
+
+    # def twoSum(self, nums, target):
+    #     # hash 1
+    #     hash_nums = {}
+    #     for index, num in enumerate(nums):
+    #         try:
+    #             hash_nums[num].append(index)
+    #         except KeyError:
+    #             hash_nums[num] = [index]
+    #     for index, num in enumerate(nums):
+    #         another = target - num
+    #         try:
+    #             candicate = hash_nums[another]
+    #             if another == num:
+    #                 if len(candicate) > 1:
+    #                     return candicate
+    #                 else:
+    #                     continue
+    #             else:
+    #                 return [index, candicate[0]]
+    #         except KeyError:
+    #             pass
+
+    # def twoSum(self, nums, target):
+    #     # hash 2
+    #     hash_nums = {}
+    #     for index, num in enumerate(nums):
+    #         another = target - num
+    #         try:
+    #             hash_nums[another]
+    #             return [hash_nums[another], index]
+    #         except KeyError:
+    #             hash_nums[num] = index
+
+    def twoSum(self, nums, target):
+        # two point
+        nums_index = [(v, index) for index, v in enumerate(nums)]
+        nums_index.sort()
+        begin, end = 0, len(nums) - 1
+        while begin < end:
+            curr = nums_index[begin][0] + nums_index[end][0]
+            if curr == target:
+                return [nums_index[begin][1], nums_index[end][1]]
+            elif curr < target:
+                begin += 1
+            else:
+                end -= 1
+
+
+if __name__ == '__main__':
+    # begin
+    s = Solution()
+    print s.twoSum([3, 2, 4], 6)

002_Add_Two_Numbers.py

@@ -0,0 +1,57 @@
+# Definition for singly-linked list.
+class ListNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+
+class Solution(object):
+    # def addTwoNumbers(self, l1, l2):
+    #     """
+    #     :type l1: ListNode
+    #     :type l2: ListNode
+    #     :rtype: ListNode
+    #     """
+    #     last = 0
+    #     head = prev = None
+    #     while True:
+    #         if l2 is None and l1 is None and last == 0:
+    #             break
+    #         val = last
+    #         if l2 is not None:
+    #             val += l2.val
+    #             l2 = l2.next
+    #         if l1 is not None:
+    #             val += l1.val
+    #             l1 = l1.next
+    #         if val >= 10:
+    #             val = val % 10
+    #             last = 1
+    #         else:
+    #             last = 0
+    #         current = ListNode(val)
+    #         if prev is None:
+    #             head = current
+    #         else:
+    #             prev.next = current
+    #         prev = current
+    #     return head
+
+    def addTwoNumbers(self, l1, l2):
+        carry = 0
+        # dummy head
+        head = curr = ListNode(0)
+        while l1 or l2:
+            val = carry
+            if l1:
+                val += l1.val
+                l1 = l1.next
+            if l2:
+                val += l2.val
+                l2 = l2.next
+            curr.next = ListNode(val % 10)
+            curr = curr.next
+            carry = val / 10
+        if carry > 0:
+            curr.next = ListNode(carry)
+        return head.next

003_Longest_Substring_Without_Repeating_Characters.py

@@ -0,0 +1,71 @@
+class Solution(object):
+    # def lengthOfLongestSubstring(self, s):
+    #     """
+    #     :type s: str
+    #     :rtype: int
+    #     """
+    #     sls = len(set(s))
+    #     ls = len(s)
+    #     if ls >= 1:
+    #         max_l = 1
+    #     else:
+    #         return 0
+    #     for i in range(ls):
+    #         for j in range(i + max_l + 1, i + sls + 1):
+    #             curr = s[i:j]
+    #             c_ls = len(curr)
+    #             if len(set(curr)) != c_ls:
+    #                 break
+    #             else:
+    #                 if c_ls > max_l:
+    #                     max_l = c_ls
+    #                     if max_l == sls:
+    #                         return sls
+    #     return max_l
+
+    # def lengthOfLongestSubstring(self, s):
+    #     sls = len(set(s))
+    #     ls = len(s)
+    #     if ls >= 1:
+    #         max_l = 1
+    #     else:
+    #         return 0
+    #     for i in range(ls):
+    #         for j in reversed(range(i + max_l + 1, i + sls + 1)):
+    #             curr = s[i:j]
+    #             c_ls = len(curr)
+    #             if len(set(curr)) == c_ls:
+    #                 if c_ls > max_l:
+    #                     max_l = c_ls
+    #                     if max_l == sls:
+    #                         return sls
+    #                 break
+    #     return max_l
+
+    # def lengthOfLongestSubstring(self, s):
+    #     exist = [False] * 256
+    #     ls = len(s)
+    #     max_len = i = 0
+    #     for j in range(ls):
+    #         while(exist[ord(s[j])]):
+    #             exist[ord(s[i])] = False
+    #             i += 1
+    #         exist[ord(s[j)] = True
+    #         max_len = max(max_len, j - i + 1)
+    #     return max_len
+
+    def lengthOfLongestSubstring(self, s):
+        # https://leetcode.com/articles/longest-substring-without-repeating-characters/
+        charMap = {}
+        for i in range(256):
+            charMap[i] = -1
+        ls = len(s)
+        i = max_len = 0
+        for j in range(ls):
+            # Note that when charMap[ord(s[j])] >= i, it means that there are
+            # duplicate character in current i,j. So we need to update i.
+            if charMap[ord(s[j])] >= i:
+                i = charMap[ord(s[j])] + 1
+            charMap[ord(s[j])] = j
+            max_len = max(max_len, j - i + 1)
+        return max_len

004_Median_of_Two_Sorted_Arrays.py

@@ -0,0 +1,60 @@
+class Solution(object):
+    # def findMedianSortedArrays(self, nums1, nums2):
+    #     """
+    #     :type nums1: List[int]
+    #     :type nums2: List[int]
+    #     :rtype: float
+    #     """
+    #     p1 = p2 = 0
+    #     ls1 = len(nums1)
+    #     ls2 = len(nums2)
+    #     all_nums = []
+    #     median = 0.0
+    #     while p1 < ls1 and p2 < ls2:
+    #         if nums1[p1] < nums2[p2]:
+    #             all_nums.append(nums1[p1])
+    #             p1 += 1
+    #         else:
+    #             all_nums.append(nums2[p2])
+    #             p2 += 1
+    #     if p1 < ls1:
+    #         while p1 < ls1:
+    #             all_nums.append(nums1[p1])
+    #             p1 += 1
+    #     if p2 < ls2:
+    #         while p2 < ls2:
+    #             all_nums.append(nums2[p2])
+    #             p2 += 1
+    #     # print all_nums
+    #     if (ls1 + ls2) % 2 == 1:
+    #         median = all_nums[(ls1 + ls2) / 2]
+    #     else:
+    #         median = 1.0 * (all_nums[(ls1 + ls2) / 2] + all_nums[(ls1 + ls2) / 2 - 1]) / 2
+    #     return median
+
+    def findMedianSortedArrays(self, nums1, nums2):
+        # https://discuss.leetcode.com/topic/4996/share-my-o-log-min-m-n-solution-with-explanation
+        # https://discuss.leetcode.com/topic/16797/very-concise-o-log-min-m-n-iterative-solution-with-detailed-explanation
+        ls1, ls2 = len(nums1), len(nums2)
+        if ls1 < ls2:
+            return self.findMedianSortedArrays(nums2, nums1)
+        l, r = 0, ls2 * 2
+        while l <= r:
+            mid2 = (l + r) >> 1
+            mid1 = ls1 + ls2 - mid2
+            L1 = -sys.maxint - 1 if mid1 == 0 else nums1[(mid1 - 1) >> 1]
+            L2 = -sys.maxint - 1 if mid2 == 0 else nums2[(mid2 - 1) >> 1]
+            R1 = sys.maxint if mid1 == 2 * ls1 else nums1[mid1 >> 1]
+            R2 = sys.maxint if mid2 == 2 * ls2 else nums2[mid2 >> 1]
+            if L1 > R2:
+                l = mid2 + 1
+            elif L2 > R1:
+                r = mid2 - 1
+            else:
+                return (max(L1, L2) + min(R1, R2)) / 2.0
+
+
+if __name__ == '__main__':
+    # begin
+    s = Solution()
+    print s.findMedianSortedArrays([1, 1], [1, 2])

005_Longest_Palindromic_Substring.py

@@ -0,0 +1,88 @@
+class Solution(object):
+    def longestPalindrome(self, s):
+        """
+        :type s: str
+        :rtype: str
+        """
+        # my solution
+        # expand string according to Manacher algorithm
+        # but extend radius step by step
+        ls = len(s)
+        if ls <= 1 or len(set(s)) == 1:
+            return s
+        # create a new list like this: "abc"->"a#b#c"
+        temp_s = '#'.join('{}'.format(s))
+        # print temp_s
+        tls = len(temp_s)
+        seed = range(1, tls - 1)
+        # this table stores the max length palindrome
+        len_table = [0] * tls
+        for step in range(1, tls / 2 + 1):
+            final = []
+            for pos in seed:
+                if pos - step < 0 or pos + step >= tls:
+                    continue
+                if temp_s[pos - step] != temp_s[pos + step]:
+                    continue
+                final.append(pos)
+                if temp_s[pos - step] == '#':
+                    continue
+                len_table[pos] = step
+            seed = final
+        max_pos, max_step = 0, 0
+        for i, s in enumerate(len_table):
+            if s >= max_step:
+                max_step = s
+                max_pos = i
+        return temp_s[max_pos - max_step:max_pos + max_step + 1].translate(None, '#')
+
+    # def longestPalindrome(self, s):
+    #     # example in leetcode book
+    #     max_left, max_right = 0, 0
+    #     ls = len(s)
+    #     for i in range(ls):
+    #         len1 = self.expandAroundCenter(s, i, i)
+    #         len2 = self.expandAroundCenter(s, i, i + 1)
+    #         max_len = max(len1, len2)
+    #         if (max_len > max_right - max_left):
+    #             max_left = i - (max_len - 1) / 2
+    #             max_right = i + max_len / 2
+    #     return s[max_left:max_right + 1]
+    #
+    # def expandAroundCenter(self, s, left, right):
+    #     ls = len(s)
+    #     while (left >= 0 and right < ls and s[left] == s[right]):
+    #         left -= 1
+    #         right += 1
+    #     return right - left - 1
+
+    # def longestPalindrome(self, s):
+    #     #Manacher algorithm
+    #     #http://en.wikipedia.org/wiki/Longest_palindromic_substring
+    #     # Transform S into T.
+    #     # For example, S = "abba", T = "^#a#b#b#a#$".
+    #     # ^ and $ signs are sentinels appended to each end to avoid bounds checking
+    #     T = '#'.join('^{}$'.format(s))
+    #     n = len(T)
+    #     P = [0] * n
+    #     C = R = 0
+    #     for i in range (1, n-1):
+    #         P[i] = (R > i) and min(R - i, P[2*C - i]) # equals to i' = C - (i-C)
+    #         # Attempt to expand palindrome centered at i
+    #         while T[i + 1 + P[i]] == T[i - 1 - P[i]]:
+    #             P[i] += 1
+    #
+    #         # If palindrome centered at i expand past R,
+    #         # adjust center based on expanded palindrome.
+    #         if i + P[i] > R:
+    #             C, R = i, i + P[i]
+    #
+    #     # Find the maximum element in P.
+    #     maxLen, centerIndex = max((n, i) for i, n in enumerate(P))
+    #     return s[(centerIndex - maxLen)//2: (centerIndex + maxLen)//2]
+
+
+if __name__ == '__main__':
+    # begin
+    s = Solution()
+    print s.longestPalindrome("abcbe")