LeetCode-Solution

Input: 100
Output: "202"

**Note:**
The input will be in range of [-1e7, 1e7].

**Tags:** [no tags]


## 思路 1
判断一下0的情况和负数的符号
kotlin(192ms/100.00%):
```kotlin
class Solution {
    fun convertToBase7(num: Int): String {
        if (num == 0) return "0"
        val isPositive = num >= 0
        var n = Math.abs(num)
        val sb = StringBuilder()
        while (n > 0) {
            sb.append(n % 7)
            n /= 7
        }
        sb.append(if (isPositive) "" else "-")
        return sb.reverse().toString()
    }
}