当输入为“1200”和“1300”时，如何使输出为“1”？

Question

运行此代码并将startn 输入1200 并将endn 输入1300 时，输出为Years:0。在哪里通过给定的测试应该是Years:1。请注意，代码运行时不会出错，并且可以与其他数字一起使用。

#include <cs50.h>
#include <stdio.h>



int main(void)
{
    int startn;
    int endn;

    do
    {
    startn = get_int("what should the starting number of llamas be?\n");
    endn = get_int("what should the ending number of llamas be?\n");
    }
    while (startn < 9 || endn < startn);


    float total = (startn + startn/3 - startn/4);
    float finalTotal = total;
    int n=0;
    
    
    while (finalTotal<endn)
    {
        finalTotal = (finalTotal + finalTotal/3 - finalTotal/4);
        n++;
    }


    printf("Years: %i\n", n);
}

代码的目的是计算到达给定的骆驼最终种群endn 所需的年数，并从给定的骆驼种群开始。在这样做的同时，我们添加了出生的美洲驼+ finalTotal/3 并删除了死亡的美洲驼- finalTotal/4。然后将总数保存在finalTotal

Answer 1

如果你用startn 初始化finalTotal，那么它将起作用。您的代码如下所示：

#include <cs50.h>
#include <stdio.h>



int main(void)
{
    int startn;
    int endn;

    do
    {
    startn = get_int("what should the starting number of llamas be?\n");
    endn = get_int("what should the ending number of llamas be?\n");
    }
    while (startn < 9 || endn < startn);

    float finalTotal = startn;
    int n=0;

    while (finalTotal<endn)
    {
        finalTotal = finalTotal + (int)(finalTotal/3) - (int)(finalTotal/4);
        n++;
    }

    printf("Years: %i\n", n);
}

您手动计算了第一年，因此它从未进入最后一个 while 。

此外，您也应该将美洲驼视为整数，而不是浮点数。 经过一点重构和更合适的变量名称后，代码如下所示：

#include <cs50.h>
#include <stdio.h>


int main(void)
{
    int start_num;
    int end_num;

    do
    {
        start_num = get_int("what should the starting number of llamas be?\n");
        end_num = get_int("what should the ending number of llamas be?\n");
    }
    while (start_num < 9 || end_num < start_num);

    int current_num = start_num;
    int years = 0;

    while (current_num < end_num)
    {
        int new_borns = current_num / 3;
        int deaths = current_num / 4;
        current_num = current_num + new_borns - deaths;
        years++;
    }

    printf("Years: %i\n", years);
}