Input: num = -7
Output: "-10"

Constraints

-10^7 <= num <= 10^7

Solution

Method 1 – Repeated Division (Base Conversion)

Intuition

To convert a decimal number to base 7, repeatedly divide the number by 7 and collect the remainders. The remainders, read in reverse order, form the base 7 representation. Handle negative numbers by converting the absolute value and adding a minus sign if needed.

Approach

If num is 0, return "0".
Record if num is negative; work with its absolute value.
While num is greater than 0:

Divide num by 7, store the remainder.
Update num to the quotient.
Append the remainder to a result list or string.

Reverse the collected digits.
Add a minus sign if the original number was negative.
Return the result as a string.

Code

[{"language":"C++","code":"class Solution {\npublic:\n   string convertToBase7(int num) {\n      if (num == 0) return \"0\";\n      bool neg = num < 0;\n      num = abs(num);\n      string ans;\n      while (num > 0) {\n        ans += to_string(num % 7);\n        num /= 7;\n      }\n      if (neg) ans += '-';\n      reverse(ans.begin(), ans.end());\n      return ans;\n   }\n};","lang":"cpp","html":"<pre class=\"shiki shiki-themes github-light github-dark\" style=\"backgrou

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