将char数组元素转换为大写或小写 [英] convert char array elemnts to upper or lower case

问题描述

对于我的家庭作业，我们要求从用户处获取一个字符串，并且:

For my homework assignment we are asked to get a string from the user and:

1. 将其全部转换为大写=已完成
2. 将其全部转换为小写=已完成
3. 将每个字符从上到下转换，反之亦然.(问题)

我不知道我的逻辑是错误的还是简单的解决方法.任何建议表示赞赏.

I do not know if my logic is wrong or if it's a simple fix. Any suggestions are appreciated.

#include <stdio.h>


int main()
{
int i;
char sentense [30];
printf("Please enter a sentence\n");
fgets(sentense, 30, stdin);

for(i=0; sentense[i] != '\0'; i++)
{
    putchar(toupper(sentense[i]));
}

for(i=0; sentense[i] != '\0'; i++)
{
    putchar(tolower(sentense[i]));
}

for(i=0; sentense[i] != '\0'; i++)
{
    if(sentense[i] >='65' && sentense[i] <='90')
    {
        putchar(tolower(sentense[i]));
    }


    else if(sentense[i] >= '97' && sentense[i] <='122')
    {
        putchar(tolower(sentense[i]));
    }
    else
    {

    }
}



return 0;
}

推荐答案

您需要更改

if(sentense[i] >='65' && sentense[i] <='90')

到

if(sentense[i] >= 65 && sentense[i] <= 90)

和休息情况，因为我们想在这里比较整数值.

and rest case(s) as we want to compare the integer value here.

启用编译器警告，您的编译器应警告您有关错误.

Enable the compiler warning and your compiler should be warning you about the mistake.

或者，您也可以使用 isupper()/ islower() 库函数也是如此.

Alternatively, you can also make use of isupper()/islower() library functions, too.

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