以下是这段时间抽时间刷的前5题，都是自己想的解法，或许不是最优解，只是整理下，方便日后优化提升

1. Two Sum：

class Solution:    # @return a tuple, (index1, index2)    def twoSum(self, num, target):        dict = {}        for i in xrange(len(num)):            if dict.get(target-num[i], None) == None:                dict[num[i]] = i            else:                return (dict[target-num[i]] , i )

2. Add Two Numbers：

class Solution(object):    def addTwoNumbers(self, l1, l2):        """        :type l1: ListNode        :type l2: ListNode        :rtype: ListNode        """        more=0        l3=ListNode(0)                l3.val=l1.val+l2.val+more        if l3.val>=10:            more=1        else:            more=0        l3.val=l3.val%10        l1_temp=l3        l1=l1.next        l2=l2.next                while(l1 and l2):            temp=ListNode(0)            temp.val=l1.val+l2.val+more            if temp.val>=10:                more=1            else:                more=0            temp.val=temp.val%10                        l1_temp.next=temp            l1_temp=temp            l1=l1.next            l2=l2.next                if((l1 is None )and( l2 is None)):            if more==1:                temp=ListNode(0)                temp.val=1                l1_temp.next=temp            return l3                    elif(l1 and ( l2 is None)):            while(l1):                temp=ListNode(0)                temp.val=more+l1.val                if temp.val>=10:                    more=1                else:                    more=0                temp.val=temp.val%10                l1_temp.next=temp                l1_temp=temp                l1=l1.next            if more==1:                temp=ListNode(0)                temp.val=1                l1_temp.next=temp            return l3                elif(l2 and ( l1 is None)):            while(l2):                temp=ListNode(0)                temp.val=more+l2.val                if temp.val>=10:                    more=1                else:                    more=0                temp.val=temp.val%10                l1_temp.next=temp                l1_temp=temp                l2=l2.next            if more==1:                temp=ListNode(0)                temp.val=1                l1_temp.next=temp            return l3

3. Longest Substring Without Repeating Characters：

class Solution(object):    def lengthOfLongestSubstring(self, s):        """        :type s: str        :rtype: int        """        new_str = ''        max = 0        for ch in s:            if not ch in new_str:                new_str += ch            else:                max = len(new_str) if len(new_str) > max else max                idx = new_str.find(ch)                new_str = new_str[idx+1:] + ch        max = len(new_str) if len(new_str) > max else max        return max

4. Median of Two Sorted Arrays：

class Solution(object):    def findMedianSortedArrays(self, nums1, nums2):        """        :type nums1: List[int]        :type nums2: List[int]        :rtype: float        """        end1=len(nums1)-1        end2=len(nums2)-1        if len(nums1)==0:            num=len(nums2)            if num%2:     #num是一个奇数                return float(nums2[num/2])            else:                median=num/2                return (float(nums2[median-1])+nums2[median])/2                    elif len(nums2)==0:            num=len(nums1)            if num%2:     #num是一个奇数                median=num/2                return float(nums1[median])            else:                median=num/2                return (float(nums1[median-1])+nums1[median])/2                        elif nums1[end1]
     
      nums2[end2]:            nums2.extend(nums1)            num=len(nums2)            if num%2:     #num是一个奇数                return float(nums2[num/2])            else:                median=num/2                return (float(nums2[median-1])+nums2[median])/2                else:            i=0            j=0            new=[]            while i
     

5. Longest Palindromic Substring：

class Solution(object):        def longestPalindrome(self, s):        """        :type s: str        :rtype: str        """        if len(s)==1:            return s        elif len(s)==2 and s[0]==s[1]:            return s        else:            s_fin1=""            s_fin2=""                        index_l=0            index_r=1            max_length=0            left=-1            right=-1            flag=0            while index_r
     
      =0 and index_r+i
      
       max_length:                    max_length=length                    left=index_l                    right=index_r                index_l=index_l+1                index_r=index_r+1            if max_length:                begin=left-max_length/2+1                end=right+max_length/2                flag=2                s_fin1=s[begin:end]                                    index=1            max_length=1            center=-1            flag=0            while index<(len(s)-1):                i=1                length=1                while index-i>=0 and index+i
       
        max_length:                    max_length=length                    center=index                index=index+1            if max_length>1:                begin=center-(max_length-1)/2                end=center+(max_length-1)/2+1                flag=1                s_fin2=s[begin:end]                            if len(s_fin1)>len(s_fin2):                return s_fin1            else:                return s_fin2