leetcode：1-5题代码整理

Posted 2020-08-08 soulmate1023

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[0]:
            nums1.extend(nums2)
            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[0]>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<len(nums1) and j<len(nums2):
                if nums1[i]<nums2[j]:
                    new.append(nums1[i])
                    i=i+1
                elif nums1[i]==nums2[j]:
                    new.append(nums1[i])
                    new.append(nums1[i])
                    i=i+1
                    j=j+1
                else:
                    new.append(nums2[j])
                    j=j+1
            while i<len(nums1):
                new.append(nums1[i])
                i=i+1
            while j<len(nums2):
                new.append(nums2[j])
                j=j+1
            num=len(new)
            if num%2:     #num是一个奇数
                return float(new[num/2])
            else:
                median=num/2
                return (float(new[median-1])+new[median])/2

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<len(s):
                i=0
                length=0
                while index_l-i>=0 and index_r+i<len(s) and s[index_l-i]==s[index_r+i]:
                    i=i+1
                    length=length+2
                if length>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<len(s) and s[index-i]==s[index+i]:
                    i=i+1
                    length=length+2
                if length>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