Description： Given an integer, return its base 7 string representation.
Example 1:
Input: 100
Output: "202"
Example 2:
Input: -7
Output: "-10"
Note: The input will be in range of [-1e7, 1e7].
题意：给定一个数，输出其7进制表示；
解法：就像计算二进制表示一样，用7去整除这个数，保存其余数；
Java
class Solution {
public String convertToBase7(int num) {
if (num == 0) return "0";
int symbol = num >= 0 ? 1 : -1;
StringBuilder sb = new StringBuilder();
num = Math.abs(num);
while (num > 0) {
sb.insert(0, num % 7);
num /= 7;
}
if (symbol == -1) sb.insert(0, "-");
return sb.toString();
}
}
