c - 如何用C解析美元和美分

假设我有一个3.50（字符串）的输入，如何解析它以便将其存储为3美元和50美分。美元和美分都是整数，并且不允许atoi。

我考虑到这一点，但显然在C语言中不起作用（假设令牌为3.50）：

dollars = int(token); /* dollars is 3 */
cents = atoi(token) - dollars; /* atoi is not allowed but I can't think of anything else */

谢谢！

最佳答案

您将需要修改它们以优雅地处理无效输入，但是这些功能将对有效输入起作用：

int get_dollars(char *str)
{
    int i = 0;
    int accum = 0;

    // While the current character is neither the null-terminator nor a '.' character
    while(str[i]&&str[i]!='.')
    {
        // Shift any previously accumulated values up one place-value by multiplying it by 10
        accum *= 10;
        // Add the numeric value of the character representation of the digit in str[i] to accum
        // (('0'-'9')-0x30=integer value 0-9)
        accum+=str[i]-0x30;
        // Increment the loop counter
        i++;
    }
    // Return the result
    return accum;
}

int get_cents(char *str)
{
    int i = 0;
    int accum = 0;
    int start_pos = 0;
    // Get the location of the '.' character so we know where the cent portion begins at
    while(str[i]&&str[i]!='.') {i++; start_pos++; }
    i = start_pos+1;
    // Same algorithm as get_dollars, except starting after the '.' rather than before
    while(str[i])
    {
        accum *= 10;
        accum += str[i]-0x30;
        i++;
    }
    return accum;
}