题目序号

2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807.

def addTwoNumbers(self, l1, l2):
    dummy = cur = ListNode(0)
    carry = 0
    while l1 or l2 or carry:
        if l1:
            carry += l1.val
            l1 = l1.next
        if l2:
            carry += l2.val
            l2 = l2.next
        cur.next = ListNode(carry%10)
        cur = cur.next
        carry //= 10
    return dummy.next

3. Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: “abcabcbb” Output: 3 Explanation: The answer is “abc”, with the length of 3. Example 2:

Input: “bbbbb” Output: 1 Explanation: The answer is “b”, with the length of 1. Example 3:

Input: “pwwkew” Output: 3 Explanation: The answer is “wke”, with the length of 3.

Note that the answer must be a substring, “pwke” is a subsequence and not a substring.

def lengthOfLongestSubstring(self, s):
    dic, res, start, = {}, 0, 0
    for i, ch in enumerate(s):
        if ch in dic:
            # update the res
            res = max(res, i-start)
            # here should be careful, like "abba"
            start = max(start, dic[ch]+1)
        dic[ch] = i
    # return should consider the last
    # non-repeated substring
    return max(res, len(s)-start)