/* leftover.cpp* 函数重载（多态）的条件：* 1）函数名必须相同* 2）函数列表必须不同（个数不同、类型不同、参数列表顺序不同）* 3）函数返回值可以相同也可以不相同* 4）仅仅返回类型不同，不足以成为函数重载*/#include <iostream>
unsigned long left(unsigned long num, unsigned ct);
char * left(const char * str, int n = 1);int main() {using namespace std;const char * trip = "Haweii!!"; // test valueunsigned long n = 12345678; // test valueint i;char * temp;for (i = 1; i < 10; i++) {cout << left(n, i) << endl;temp = left(trip, i);cout << temp << endl;delete[] temp;}return 0;
}unsigned long left(unsigned long num, unsigned ct) {unsigned digits = 1;unsigned long n = num;if (ct == 0 || num == 0)return 0;while (n /= 10)digits++;if (digits > ct) {ct = digits - ct;while (ct--)num /= 10;return num;}elsereturn num;
}char * left(const char * str, int n) {if (n < 0)n = 0;char * p = new char[n + 1];int i;for (i = 0; i < n && str[i]; i++)p[i] = str[i];while (i <= n)p[i++] = '\0';return p;
}