Printing missing numbers from given input

Question

Numbers which are in sequence in ascending order are given as a input as string.The program should print the missing number ?

EX:

INPUT

567568600601602

OUTPUT

569

EXPLANATION

567,568,600,601,602 are the numbers in sequence and 569 is the missing number

INPUT

1112131516

OUTPUT

14

EXPLANATION

11,12,13,15,16 are the numbers in sequence and 569 is the missing

MY CODE

a=input()
a=a.rstrip()
b=list(set(a))
l=[]
p=[]
c=0
for i in range(len(b)):
    if a.count(b[i])>1:
        c+=1
j=0
while j<=len(a):
    l.append(a[j:j+c+1])
    j=j+c+1
del l[-1]
k=int(l[0])
while k<=int(l[-1]):
    p.append(k)
    k=k+1
for u in range(len(p)):
    if str(p[u]) not in l:
        print(p[u])
        break

My query:

My program is unable to find the missing number in case of 2 or 4 digit numbers given as input in form of string .

input 6768707172
output of my program 677
expected output 69

How to check the whether the string has 2 or 3 or 4 digit numbers and break them accordingly ?

FcoRodr · Accepted Answer

I just made this approach for fun and it seems to work (I'm not controling bad input exceptions and it can surely be improved). I basically start from 1 char lenght and try if I'm right.

I hope it helps:

MAX_LEN = 6

def findMissingNumber(s):
    print 'Input received: ' + s

    for digitsNumber in range(1,MAX_LEN+1):
        print 
        # Initializing stuff
        index = digitsNumber
        currentNumber = int(s[:digitsNumber])
        exit = False
        missing = None

        while not exit and index < len(s):
            # Store expected next number
            nextNumber = currentNumber + 1
            # Store expected next number length
            nextNumberLen  = len(str(nextNumber))
            # Store next number in the provided string
            # based the lenght of the expected number
            nextStringNumber = int(s[index : index + nextNumberLen])
            print 'Have ' + str(currentNumber) + ', expecting ' + str([nextNumber,nextNumber+1]) + ' and got ' + str(nextStringNumber)
            # Check if number gotten is the next or the following
            if nextStringNumber in [nextNumber, nextNumber+1]: 
                # Check if number is not the next
                # (means there is a number missing)
                if nextStringNumber != nextNumber:
                    # Check if there was a previous missing number
                    if not missing:
                        print 'Found missing ' + str(nextNumber)
                        missing = nextNumber
                    # If there was, exit  and forget missing number
                    # (only 1 missing number allowed)
                    else:
                        print 'More than 1 missing, exit'
                        missing = None
                        exit = True
                # Set stuff for next iteration
                currentNumber = nextStringNumber
                index += nextNumberLen
            # If end of string, exit
            else:
                print 'End of string, exit'
                exit = True
        # If only 1 missing found, return it
        if missing:
            print 'Returning ' + str(missing)
            return missing
        print 'Going to next number lenght'
    # If no missing found, return -1
    return -1

findMissingNumber('6768707172')

Giving as a result:

Input received: 6768707172

Have 6, expecting [7, 8] and got 7
Have 7, expecting [8, 9] and got 6
End of string, exit
Going to next number lenght

Have 67, expecting [68, 69] and got 68
Have 68, expecting [69, 70] and got 70
Found missing 69
Have 70, expecting [71, 72] and got 71
Have 71, expecting [72, 73] and got 72
Returning 69

Printing missing numbers from given input

Answers (2)

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