[英]C: comparing two strings from a struct
我几乎是C语言的新手,我想知道如何比较两个单独的struct成员变量的字符串。 也许提供我的代码将使我的要求变得清晰。
我有以下结构:
typedef struct mentry {
char *surname;
int house_number;
char *postcode;
char *full_address;
} MEntry;
我想比较两个单独的MEntry变量。 我想检查两个条目的姓氏是否相同。 因此,我编写了以下方法:
int me_compare(MEntry *me1, MEntry *me2)
{
int surnameResult;
char me1Surname = *(me1->surname);
char me2Surname = *(me2->surname);
surnameResult = strcmp(me1Surname, me2Surname);
return surnameResult;
}
编译程序时,我收到以下消息:
mentry.c:30:6: warning: passing argument 1 of ‘strcmp’ makes pointer from integer without a cast [enabled by default]
surnameResult = strcmp(me1Surname, me2Surname);
我认为这行是错误的:
char me1Surname = *(me1->surname);
设置me1Surname等于姓氏的值,而不是姓氏的地址?
我还收到另一条警告说:
"In file included from mentry.c:2:0:
/usr/include/string.h:140:12:note: expected ‘const char *’ but argument is of type ‘char’
extern int strcmp (const char *__s1, const char *__s2)"
有人可以解释为什么出现此警告吗?
您正在努力:
尝试显而易见的方法:
int me_compare(const MEntry *me1, const MEntry *me2)
{
return strcmp(me1->surname, me2->surname);
}
比较字符串而不使用字符串库。 如果相同,则此方法比较字符串,如果两个字符串相等,则返回值0。 传入方法内部的struct指针即可。
int compareStr(char *s, char *t)
{
char t1 = *s;
char t2 = *t;
int x;
while (t1 != '\0' && t2 != '\0') {
x = (int)(t1 - t2);
if (x ==0) {
s++;
t++;
t1 = *s;
t2 = *t;
}
else
{
break;
}
}
return x;
}
您可以尝试这个简单的示例。 只需要使两个MEntry
结构对象对其进行测试,并通过使用它们的地址来比较结构中的指针姓氏即可。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
char *surname;
int house_number;
char *postcode;
char *full_address;
} MEntry;
int me_compare(MEntry *me1, MEntry *me2);
int
main(void) {
MEntry me1 = {"McLeod", 27, "3432", "27 Baker Street, London"};
MEntry me2 = {"Baggins", 19, "3242", "145 Bag End, Shire"};
if (me_compare(&me1, &me2) == 0) {
printf("Surnames are identical.\n");
} else {
printf("Surnames are different.\n");
}
return 0;
}
int
me_compare(MEntry *me1, MEntry *me2) {
int surnameResult;
surnameResult = strcmp(me1->surname, me2->surname);
return surnameResult;
}
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