我的字符串比较在 Cpp 中不起作用答案

【问题标题】：My String compare isn't working in Cpp我的字符串比较在 Cpp 中不起作用
【发布时间】：2013-11-11 17:38:53
【问题描述】：

// 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
}

于是我在cpp中写了一个字符串比较的方法，搞不明白是什么问题。

【问题讨论】：

|| 应该是 &&。然后你需要稍微重写一下逻辑。在您在该行上方评论中的非常示例中，您将超出if 条件的范围。
我正要说明错误，但我敢打赌 Simple 拥有它的权利。
另外，如果两个字符串的长度不同？
在什么输入中它不起作用？任何或特殊情况？是否存在误报、误报或两者兼有？
当我在 2 个字符串 '\0' 和 'foobar\0' 上运行该方法时，它返回 0 而不是 f 和 '\0' 之间的差异

标签： c++ string

【解决方案1】：

只要其他人正在显示代码，这就是我对此的看法。没有必要不断地将第一个和第二个字符与 0 进行比较，然后再相互比较。一旦两个字符之一为 0，您就完成了，您可以返回差值r。 r 不需要被初始化，因为while 测试的第二部分总是被执行——它是一个和，所以这两个部分都需要为真。

另外值得注意的是：我看到我本能地反转了结果的符号。在比较字符串 A 和 B 时，您可能想知道“A 是否小于比 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;
}

【讨论】：

【解决方案2】：

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
}

【讨论】：

【解决方案3】：

据我所知，您的功能很好。特别是，它确实适用于您说它不起作用的示例：

#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"));
}

这会按预期打印一个负数。

（我已重命名函数，以免混淆 strcmp() 被调用。我建议您也这样做。）

【讨论】：