Question

// Compares the two arguments.  If they are equal, 0 is returned.  If they
// are not equal, the difference of the first unequal pair of characters
// is returned.
int strcmp(const char* charPointerToArray1, const char* charPointerToArray2) {
    int i = 0;
    // we need to check if both arrays have reached their terminating character
    // because consider the case where array1 = { '\0' } and array2 = { '1', '\0' }
    while (charPointerToArray1[i] != '\0' || charPointerToArray2[i] != '\0') {
        // while iterating through both char arrays,
        // if 1 char difference is found, the 2 char arrays are not equal
        if (charPointerToArray1[i] != charPointerToArray2[i]) {
            int differenceOfFirstUnequalChars = charPointerToArray1[i] - charPointerToArray2[i];
            return differenceOfFirstUnequalChars;
        } else {
            i++;
        }
    }
    return 0; // charPointerToArray1 == charPointerToArray2
}

所以我在Cpp中写了一个字符串比较方法，我无法弄清楚是什么问题。

Answer 1

只要其他人显示代码，这是我对此的看法。不需要继续将第一和第二字符比较为0，然后相互比较。只要两个字符中的一个为0，您就完成了，您可以返回差异r。 r无需初始化，因为while测试的第二部分始终执行 - 它是和，因此两个部分都必须为true。

同样值得注意的是：我看到我本能地扭转了结果的征兆。将字符串A与B进行比较时，您可能想知道“A是小于而不是B”，这将由否定结果表示。

#include <stdio.h>

int my_strcmp (const char* charPointerToArray1, const char* charPointerToArray2)
{
    int i = 0, r;
    while ((charPointerToArray1[i] || charPointerToArray2[i]) &&
        !(r = (charPointerToArray2[i] - charPointerToArray1[i])))
    {
        i++;
    }
    return r;
}

int main (void)
{
    printf("%d\n", my_strcmp("foobar", ""));
    printf("%d\n", my_strcmp("foobar", "foobaz"));
    printf("%d\n", my_strcmp("foobar", "foobar"));
    return 0;
}

Answer 2

据我所知，你的功能很好。特别是，它确实适用于你说它没有的例子：

#include <stdio.h>

int my_strcmp(const char* charPointerToArray1, const char* charPointerToArray2) {
    int i = 0;
    // we need to check if both arrays have reached their terminating character
    // because consider the case where array1 = { '\0' } and array2 = { '1', '\0' }
    while (charPointerToArray1[i] != '\0' || charPointerToArray2[i] != '\0') {
        // while iterating through both char arrays,
        // if 1 char difference is found, the 2 char arrays are not equal
        if (charPointerToArray1[i] != charPointerToArray2[i]) {
            int differenceOfFirstUnequalChars = charPointerToArray1[i] - charPointerToArray2[i];
            return differenceOfFirstUnequalChars;
        } else {
            i++;
        }
    }
    return 0; // charPointerToArray1 == charPointerToArray2
}


int main() {
  printf("%d\n", my_strcmp("", "foobar"));
}

这会打印一个预期的负数。

（我已经重命名了这个函数，以便不会混淆strcmp()被调用。我建议你这样做。）

Answer 3

这是工作示例：

// Compares the two arguments.  If they are equal, 0 is returned.  If they
// are not equal, the difference of the first unequal pair of characters
// is returned.
int strcmp(const char* charPointerToArray1, const char* charPointerToArray2) {
    int i = 0;
    // we need to check if both arrays have reached their terminating character
    // because consider the case where array1 = { '\0' } and array2 = { '1', '\0' }
    while (charPointerToArray1[i] != '\0' && charPointerToArray2[i] != '\0') {
        // while iterating through both char arrays,
        // if 1 char difference is found, the 2 char arrays are not equal
        if (charPointerToArray1[i] != charPointerToArray2[i]) {
            int differenceOfFirstUnequalChars = charPointerToArray1[i] - charPointerToArray2[i];
            return differenceOfFirstUnequalChars;
        } else {
            i++;
        }
    }
    // return 0; // not really, one of the array may be longer than the other
    if (charPointerToArray1[i] == '\0' && charPointerToArray2[i] == '\0')
        return 0;
    else //... one of the array is longer
}

我的字符串比较在Cpp中不起作用

3 个答案: