{"id":864,"date":"2020-06-11T10:14:32","date_gmt":"2020-06-11T10:14:32","guid":{"rendered":"https:\/\/blog.prepbytes.com\/?p=864"},"modified":"2023-11-27T05:07:15","modified_gmt":"2023-11-27T05:07:15","slug":"find-the-missing-number-in-sequence-given-as-string","status":"publish","type":"post","link":"https:\/\/prepbytes.com\/blog\/find-the-missing-number-in-sequence-given-as-string\/","title":{"rendered":"Find the missing number in sequence given as string"},"content":{"rendered":"

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\nIn the realm of problem-solving and data manipulation, uncovering the missing element in a sequence embedded within a string can be a perplexing yet intriguing task. This article delves into strategies and algorithms to detect and retrieve the absent number within a sequence represented as a string. Whether the sequence follows a numerical, alphabetical, or pattern-based structure, exploring methodologies to decipher the missing element plays a pivotal role in algorithmic thinking and programming prowess.<\/p>\n

How to Find a Missing Number in a Sequence?How to Find a Missing Number in a Sequence?<\/h2>\n

Find the missing number in a given in a series as a string with no separator. The maximum length of the number can go up to 6 only. Print -1 if the sequence is invalid, or sequence skips number more than 1 place.<\/p>\n

<\/strong><\/u><\/a><\/p>\n

Test Case:<\/h4>\n
    Input:\n    4\n    1234578\n    1314151618\n    123124125127\n    1213141718\n\n    Output:\n    6\n    17\n    126\n    -1\n\n    Explanation:\n    Case-1:\n        Given sequence is \"1 2 3 4 5 7 8\" where 6 is missing from sequence, so 6 is our answer.\n    Case-2:\n        Given sequence is \"13 14 15 16 18\" where 17 is missing from sequence, so 17 is our answer.\n    Case-3:\n        Given sequence is \"123 124 125 127\" where 126 is missing from sequence, so 126 is our answer.\n    Case-4:\n        Given sequence is \"12 13 14 17 18\" where 6 and 7 are missing from sequence, gap can be only of one number so it is an invalid sequence, so -1 is our answer.<\/code><\/pre>\n
Solving Approach :<\/h3>\n
\n
1) As we know the maximum length of the number goes up to 6, so we can check the number of all lengths from 1 to 6.
\n2) For each length, we convert numbers of length from string to integer and check if any number is missing from the sequence, if yes we print the number.
\n3) If the sequence has more than 1 number missing or number have a difference more than 1, that means sequence is invalid. So, we print -1 in this case.
\n4) Exceptions occur when the number of digits changes when moving to the next number, for example moving from 99 to 100, we use log\u2081\u2080A values in such cases, to notice the change in digits.<\/p>\n<\/blockquote>\n
Example:<\/h3>\n
\n
    \n
  • \n
    Test Case – 1:<\/em><\/strong><\/p>\n
    Let string s = "12356",
    \nFinding all values of length 1 first,
    \nconverting all digits of length 1 in number, we get these values,<\/p>\n
    1,2,3,5,6<\/p>\n
    As we can see 4 is missing, we print 4 as our result, and we don’t need to check further.<\/p>\n<\/li>\n
  • \n
    Test Case – 2:<\/em><\/strong><\/p>\n
    Let string s = "1112131516",
    \nFinding all values of length 1 first, we get these values,
    \n1,1,1,2,1,3,1,5,1,6
    \nAs we can see this series does not make a sequence, we check for all numbers of length 2, Thus, we get this >sequence,
    \n11,12,13,15,16
    \nAs we can see, this sequence lacks 14, hence 14 is our answer and we do not proceed further.<\/p>\n<\/li>\n
  • \n
    Test Case – 3:<\/em><\/strong>
    \nLet string s = "9899100102"
    \nWe start checking for all values of length 1, thus we get this sequence,
    \n98,99,10
    \nWhile reading 10 we get the value of $log_{10}(10)$ which is 1, meaning length has to be increased by 1, and from here we check for number with length 2+1 i.e. 3, hence the sequence becomes,
    \n98,99,100,102
    \nWe can see this sequence lacks 101, so we print 101 as our answer.<\/p>\n<\/li>\n<\/ul>\n<\/blockquote>\n
    Solutions<\/h3>\n\t\t\t\t\t\t