题目要求：
给定一个整数 num，将其转化为 7 进制，并以字符串形式输出。
C++源码：
#include "stdafx.h"
#include <String>
using namespace std;string convertToBase7(int num) {int tempNum = num;char t;string str;if (tempNum == 0) return "0";if (tempNum<0){tempNum = -tempNum; }while (tempNum >= 7){t = (tempNum % 7); tempNum /= 7; str.insert(0, to_string(t)); }t = tempNum;str.insert(0, to_string(t)); if (num<0){str.insert(0, "-");}return str;
}int _tmain(int argc, _TCHAR* argv[])
{string st = convertToBase7(7);printf(st.c_str());printf("\n");st = convertToBase7(14);printf(st.c_str());printf("\n");st = convertToBase7(700);printf(st.c_str());printf("\n");st = convertToBase7(777);printf(st.c_str());printf("\n");return 0;
}运行的结果：
