405. Convert a Number to Hexadecimal

Sun, 14 Apr 2024 21:06:34 +0800

Intuition

Just use the transformation algorithm from decimal to hexadecimal

Approach

Simulation by doing the following:

compute remain = num % 16, add remain to the result (push_back)
update num = (num - remainder) / 16
repeat step 1 and step 2 until num is 0

Notice that when num < 0, we need use its complement.

Complexity

Time complexity: the loop depends on the number of digits of num.
$$O(\log n)$$
Space complexity:
$$ O(1) $$

Code

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class Solution {
public:
 string toHex(long num) {
 if (num == 0) return "0";
 if (num < 0) num = INT_MAX + num + 2 + INT_MAX;
 string result;
 while (num) {
 int divide = num % 16;
 num = (num - divide) / 16;
 if (divide < 10) result += ('0' + divide);
 else result += ('a' + (divide - 10));
 }
 reverse(result.begin(), result.end());
 return result;
 }
};

Math on Jiang Yi(姜祎)'s Homepage

405. Convert a Number to Hexadecimal

Intuition

Approach

Complexity

Code