Question

我编写了一个代码，可以打印出用户输入字符串中有多少个 a。

我希望程序打印出“总共有 1 个 a”而不是“总共有 1 个 a”。

我尝试编写一个 if 语句，但它会在每个循环中打印出字符串的长度。我该如何调整？我已经尝试了一些东西，但我没有达到那个程度。

#include <stdio.h>
#include <cs50.h>
#include <string.h>

int main(void){
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");

    for (int i = 0, n = strlen(input); i < n ; i++){
        if (input[i] == 'a' || input[i] == 'A'){
             count++;
        }
        if (count == 1){
            printf("\nThere is a total of %i a", count);
        }
    }

    printf("\nThere are a total of %i a's", count);
}

Answer 1

#include <stdio.h>
#include <cs50.h>
#include <string.h>

int main(void){
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");

for (int i = 0, n = strlen(input); i < n ; i++)
        if ((input[i] | 0x20) == 'a')
            count++;

    (count == 1) ? printf("\nThere is a total of 1 a") : printf("\nThere are a total of %i a's", count);

}

使用 ternary operator。

注意：('a' 或 0x20) 以及 ('A' 或 0x20) 等于 'a'

Answer 2

您可以使用 if 语句来编写。

#include <stdio.h>
#include <cs50.h>
#include <string.h>

int main(void){
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");

    for ( size_t i = 0, n = strlen(input); i < n ; i++){
        if (input[i] == 'a' || input[i] == 'A'){
             count++;
        }
    }

    if (count == 1){
        printf("\nThere is a total of %i a", count);
    }
    else {
        printf("\nThere are a total of %i a's", count);
    }
}

或者你可以使用条件运算符

#include <stdio.h>
#include <cs50.h>
#include <string.h>

int main(void){
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");

    for ( size_t i = 0, n = strlen(input); i < n ; i++){
        if (input[i] == 'a' || input[i] == 'A'){
             count++;
        }
    }


    printf("\nThere %s a total of %i a%s", 
           count == 1 ? "is" : "are", 
           count, 
           count == 1 ? "" : "'s" );
}

第三种方法可以使用指定格式字符串的字符串文字。例如

#include <stdio.h>
#include <cs50.h>
#include <string.h>

int main(void){
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");

    for ( size_t i = 0, n = strlen(input); i < n ; i++){
        if (input[i] == 'a' || input[i] == 'A'){
             count++;
        }
    }

    string format;

    if (count == 1){
        format = "\nThere is a total of %i a";
    }
    else {
        format = "\nThere are a total of %i a's";
    }

    printf( format, count );
}

Answer 3

只需将这一行从 for 循环中取出

if (count == 1){
    printf("\nThere is a total of %i a", count);
}

然后在循环外构造一个这样的条件语句

if (count == 1){
    printf("\nThere is a total of %i a", count);
}else if(count > 1){
    printf("\nThere are a total of %i a's", count);
}else{
    printf("\nThere are no a's");
}

这就是你的最终代码应该是什么样子

int main(void){
int ctr = 0;
string input = get_string("Write something and I'll tell you how many a's there are: ");

for (int i = 0; i < strlen(input) ; i++){

    if (input[i] == 'a' || input[i] == 'A'){
         count++;
    }

    //Where you removed the if (count == 1)

}

//Where it should be
if (count == 1){
    printf("\nThere is a total of %i a", count);
}else if(count > 1){
    printf("\nThere are a total of %i a's", count);
}else{
    printf("\nThere are no a's");
}

}

Answer 4

如果你想在满足条件后退出循环，你可以使用 break 语句，它会让你退出内部循环。

Answer 5

int main(void)
{
    int count = 0;
    string input = get_string("Write something and I'll tell you how many a's there are: ");
    

    for (size_t i = 0, n = strlen(input); i < n ; i++)
        count += (input[i] == 'a' || input[i] == 'A');
    
    printf("\nThere is a total of %i a%s", count, count == 1 ? "" :"'s");

}

如果满足条件，如何将 if 语句从循环中取出？

5 个答案: