转成7进制,辗转相除。
string convertToBase7(int num) { if (num == 0) return "0"; bool neg = false; if (num < 0) { neg = true; num = -num; } string ret; int rem; while (num) { rem = num % 7; num = num / 7; ret.push_back(rem + '0'); } reverse(ret.begin(), ret.end()); if (neg) ret = "-" + ret; return ret; }