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Recursion - Easy Level - Question 1

Recursion - Easy Level - Question 1


Leetcode 504 Base 7

Given an integer num, return a string of its base 7 representation.

Constraints:

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


Analysis:

1. if abs(num) < 7, return to_string(num). For example, 0 ->  "0",  -1 -> "-1", 1 -> "1", etc.

2. otherwise, we just need to consider (num/7) and (num%7). The second part can be converted to a string directly (need to pay attention to the negative values. For example, -8. num%7 == -1, but we just need "1" actually. So need to use the abse(num%7)). The first part can be calculated recursively.


See the code below:


class Solution {
public:
    string convertToBase7(int num) {
        // base
        if(abs(num) < 7) return to_string(num);
        // converging
        return convertToBase7(num/7) + to_string(abs(num%7));
    }
};


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