为什么我指向整数数组的指针不起作用？答案

【问题标题】：Why aren't my pointers to integer arrays working?为什么我指向整数数组的指针不起作用？
【发布时间】：2013-04-01 17:31:02
【问题描述】：

这里有问题：http://cps125.scs.ryerson.ca/labs/homework8.gif

这是我的尝试：

#include <stdio.h>

void tenfold(int (*array1)[9], int (*array2)[9])
{
    int i;
    for (i = 0; i < 9; i++) {
        if ((*array1)[i] > 0) {
            (*array2)[i] = 10 * (*array1)[i];
        } else {
            (*array2)[i] = (*array1)[i];
        }
    }
}

int main()
{
    int array1[9] = { 3, 4, 5, 6, 7, -8, -9, 1, 2 }, array2[9], i;

    tenfold(&array1, &array2);

    for (i=0; i < 9; i++) {
        printf("%lf ", array2[i]);
    }
    return 0;
}

这是输出：

44100667367791664000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000.000000 441006673677917200000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000000000000000.000000 4410066736779177 6000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000.000000 4410066736779183200000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000.000000 44100667367791888000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000000000000000000000000000000.000000 441006913918453040000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000.000000 441006913918452980000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000.000000 4410066736779155 2000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000.000000 4410066736779160800000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000.000000

【问题讨论】：

标签： c arrays pointers

【解决方案1】：

这里至少有一个问题：

printf("%lf ", array2[i]);

%lf 字面意思是“长浮点数”，但是你想打印整数：

printf("%i\n", array2[i]);

还要记住 printf 等待 \n 刷新。

编辑：正如 newacct 所指出的，%f 和 %lf 最后都是 double，因为可变参数将 float 提升为 double。

【讨论】：

@user1251385 总是编译器带有-Wall 选项
如前所述，使用-W -Wall -Werror 编译可以防止此类错误的发生。也读人！
在printf中，%lf与%f相同（都是double）

【解决方案2】：

"%lf" 是浮点数的格式，而不是整数。

【讨论】：

【解决方案3】：

函数tenfold中输入数组的定义不需要加星号

只要定义如下

void tenfold(int array1[9], int array2[9])

在函数tenfold中使用array1和array2时去掉星号*

void tenfold(int array1[9], int array2[9])
{
    int i;
    for (i = 0; i < 9; i++) {
        if ((array1)[i] > 0) {
            (array2)[i] = 10 * (array1)[i];
        } else {
            (array2)[i] = (array1)[i];
        }
    }
}

当您在main 中调用tenfold 函数时：

tenfold(array1, array2);

【讨论】：