数字回文#4【难度:2级】:

答案1:

def palindrome(num): if type(num) is not int or num < 0: return "Not valid" else: c =0 for i in range(num,num**2): if is_pal(i): return i elif is_pal(i-c): return i-c else: c +=2 def is_pal(n): return n > 10 and n == int(str(n)[::-1])​

答案2:

is_palindrome = lambda x: x > 10 and str(x) == str(x)[::-1] def palindrome(num): if not isinstance(num, int) or num < 0: return "Not valid" smaller, larger = num, num while True: checks = is_palindrome(smaller), is_palindrome(larger) if checks == (True, False): return smaller if checks == (False, True): return larger if checks == (True, True): return larger smaller -= 1 larger += 1​

答案3:

def is_palindrome(n): s = str(n) return s == s[::-1] def palindrome(num): if not isinstance(num, int) or num < 0: return "Not valid" if num < 17: return 11 inf = next(n for n in range(num, 0, -1) if is_palindrome(n)) sup = next(n for n in range(num, 2*num) if is_palindrome(n)) mean = (inf + sup) / 2 return sup if num >= mean else inf​

答案4:

from itertools import count def palindrome(num): return next(c for b in count(0) for c in (num + b, num - b) if c > 9 and c == int(str(c)[::-1])) if isinstance(num, int) and num >= 0 else 'Not valid'​

答案5:

def findR(num): while True: if str(num)==str(num)[::-1]: return num num+=1 def findL(num): while True: if str(num)==str(num)[::-1]: return num num-=1 def palindrome(num): if type(num)!=int or num<0: return 'Not valid' if num<=10: return 11 else: if findR(num)-num<=num-findL(num): return findR(num) else: return findL(num) ​

答案6:

def is_pali(num): return str(num) == str(num)[::-1] and num > 9 def palindrome(num): if type(num) != int or str(num) != str(int(num)) or int(num) < 0: return 'Not valid' n = 0 if num <= 11: return 11 while n < num: test1 = num - n test2 = num + n if is_pali(test2): return num + n elif is_pali(test1): return num - n n += 1​

答案7:

""" Solution without loops ! """ """ Define the first segment of what wwould be a "not far away palindrome" based on "num" : num = 1258 -> midPart = 12 ( -> would give "1221" ) num = 459 -> midPart = 45 ( -> would give "454" ) Check for lower and upper values (in case num is near of change of decade, upperbond or lowerbond) and define 3 possible parts of palindromes: num = 1258 -> 12 -> lowPart = 11 midPart = 12 highPart = 13 num = 459 -> 45 -> lowPart = 44 midPart = 45 highPart = 46 Construct palindromes according to each part an the parity of the length of the original number: num = 1258 -> lPal = 1111 ; mPal = 1221 ; hPal = 1331 num = 459 -> lPal = 444 ; mPal = 454 ; hPal = 464 Sort the result with tuples defined as: (abs(num-newPal), -newPal) This way, the nearest new palindrome value are first, and if two values of "abs(num-newPal)" are equal, the second element of the tuple ensure to find the highest one as first element of the sorted list of tuples. return the opposite of the second element of the first tuple, which is so "newPal". Edge cases: num = 1999 -> lPal = 1881 ; mPal = 1991 ; hPal = 2002 => return 2002 num = 801 -> lPal = 797 ; mPal = 808 ; hPal = 818 => return 797 num = 1002 -> lPal = 99(!); mPal = 1001 ; hPal = 1111 => return 1001 """ def nextPal(sPart, ls): return int( sPart + sPart[:len(sPart)-ls%2][::-1] ) def palindrome(num): if type(num) != int or num <= 0: return "Not valid" s = str(num) midPart = s[:(len(s)+1)//2] lowPart = str(int(midPart)-1) highPart = str(int(midPart)+1) lPal, mPal, hPal = nextPal(lowPart, len(s)), nextPal(midPart, len(s)), nextPal(highPart, len(s)) return 11 if num <= 16 else -sorted( (abs(num-pal), -pal) for pal in [lPal, mPal, hPal] )[0][1]​

答案8:

def is_palindrome(num): if num < 10: return False s = str(num) return s[0:len(s)//2] == s[len(s)-1:len(s)-len(s)//2-1:-1] def palindrome(num): if type(num) is not int or num < 0: return 'Not valid' if is_palindrome(num): return num n = 1 while True: if is_palindrome(num + n): return num + n elif is_palindrome(num - n): return num - n n += 1 ​

答案9:

def find_palindrome(num, step = -1): while num > 10: if str(num) == str(num)[::-1]: return num num += step return -1 def palindrome(num): if not isinstance(num, int) or num <= 0: return 'Not valid' if num < 10: return 11 s = str(num) if s == s[::-1]: return num top = find_palindrome(num, 1) down = find_palindrome(num, -1) if top - num <= num - down: return top return down ​

答案10:

def is_pal(s): return s==s[::-1] and len(s)>1 def palindrome(n): if not isinstance(n,int) or n<0: return "Not valid" if is_pal(str(n)): return n i=1 while True: if is_pal(str(n+i)): return n+i if is_pal(str(n-i)): return n-i i+=1​

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