比较结构的变量

I'm not sure if I'm asking the right question. lets say we have the following

我不确定我是否在问正确的问题。我们可以说有以下内容

    typedef struct {
        char month[2];
        char day[2];
        char year[4];
    } dateT;

void dates(dateT* ptrDateList);   

int main()
{
    dateT* ptrList;
    scanf("%d", &n);//number of date entries 
    ptrList = malloc(n*sizeof(dateT));
    for (i=0; i<n; i++)
        dates(&ptrList[i]);
}

void dates(dateT* ptrDateList);
{
    char inputMonth[2];
    char inputDay[2];
    char inputYear[4];
    scanf("%s",inputMonth);
    strcpy(ptrDateList->month,inputMonth);
    scanf("%s",inputDay);
    strcpy(ptrDateList->day,inputDay);
    scanf("%s",inputYear);
    strcpy(ptrDateList->year,inputYear);
}

how you compare the value of day in ptrList[2] with lets say the value of day in ptrList[5]

你如何比较ptrList [2]中的day值与ptrList [5]中的day值相比较

I know that if I did

我知道如果我这样做了

dateT list2={5,10,2009};
dateT list5={7,10,2009};

I could do

我可以

list2.day == list5.day

but how would I do that with the arrays

但是如何使用数组做到这一点

2 个解决方案

#1

ptrList[2].day == ptrList[5].day would work if the type was say integer, but as you store the characters you might want to use strcmp, like so:

ptrList [2] .day == ptrList [5] .day可以工作,如果类型是整数,但是当你存储字符时你可能想要使用strcmp,如下所示:

if ((strcmp(ptrList[2].day,ptrList[5].day) == 0) // same day

note that you need an extra character for the end of string sentinel \0, so it should be;

请注意,字符串sentinel \ 0的结尾需要一个额外的字符,所以它应该是;

typedef struct {
        char month[3];
        char day[3];
        char year[5];
} dateT;

another issue is the way you handle input: can you be sure that the user will provide valid input? for instance you could use scanf("%2s", string); to input the day (of max. length two).

另一个问题是你处理输入的方式:你能确定用户会提供有效的输入吗?例如,你可以使用scanf(“%2s”,string);输入日期(最大长度为2)。

#2

Here's pretty much what jev already explain. Just I thought I might as well post it, since it works.

这几乎是jev已经解释过的。只是我想我也可以发布它,因为它有效。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
        char month[3];
        char day[3];
        char year[5];
    } dateT;

void dates(dateT* ptrDateList);   

int main()
{
    dateT* ptrList;
    int i, n;
    printf("Enter number of dates: "); 
    scanf("%d", &n);//number of date entries 
    ptrList = malloc(n*sizeof(dateT));
    for (i=0; i<n; i++)
        dates(&ptrList[i]);
    if (n > 1) {
        if (!strcmp(ptrList[0].day,ptrList[1].day)) {
            printf("First two days match.\n");
        } else {
            printf("First two days don't match.\n");
        }   
    }

    return 0;
}

void dates(dateT* ptrDateList)
{
    char inputMonth[3];
    char inputDay[3];
    char inputYear[5];

    printf("Enter month: "); 
    scanf("%2s",inputMonth);
    inputMonth[2] = '\0';
    strcpy(ptrDateList->month,inputMonth);

    printf("Enter Day: "); 
    scanf("%2s",inputDay);
    inputDay[2] = '\0';
    strcpy(ptrDateList->day,inputDay);

    printf("Enter Year: "); 
    scanf("%4s",inputYear);
    inputYear[4] = '\0';
    strcpy(ptrDateList->year,inputYear);
}

#1