Question

这是我向后打印字符串中每个单词的源代码。但是这段代码只是向后打印第一个单词而不是整个字符串。在向后打印第一个单词后，它会生成向后打印的第一个和第二个单词的图案。如果使用while而不是if，则会生成无限循环。

// Print an Entered String Backwards
#include <stdio.h>
#include <string.h>

int main()
{
    int j,i;
    char str[100];
    printf("Enter String\n");
    gets(str);
    printf("\nString in Reverse Order\n");
    i=0;
    while(str[i]!='\0')
    {
        if(str[i]==' ')
        {
            for(j=i-1;j>=0;j--)         //Loop starts from last char and decrements upto 0th char
                printf("%c",str[j]);
            printf(" ");
        }
        i++;
    }
}

Answer 1

请勿使用gets。它不安全，已被弃用。请改用fgets来读取输入字符串stdin。现在，要向后打印字符串中的每个单词，您需要更改while循环。

#include <stdio.h>

int main(void)
{
    int i, j;
    char str[100];
    printf("Enter String\n");

    // fgets reads one less than sizeof(str), i.e., 99
    // characters from stdin and stores them in str array.
    // it returns when a newline is input which it stores in
    // the the array and then appends a terminating null byte
    // to mark the end of the string
    fgets(str, sizeof str, stdin);
    printf("\nString in Reverse Order\n");

    i = 0;
    while(str[i] != '\0')
    {
        if(str[i] == ' ' || str[i] == '\n')
        {   
            // the loop condition checks for either the 
            // start of the string or a whitespace since
            // since these two cases demarcate a word from
            // other words in the string
            for(j = i - 1; j >= 0 && str[j] != ' '; j--)
                printf("%c", str[j]);

            printf(" ");    
        }
        i++;
    }
    // output a newline to flush the output
    printf("\n"); 
    return 0;   
}

Answer 2

您评论的循环不应该在第0个字符处结束，但应该到达最后一个空白区域（如果有的话）。

//Print an Entered String Backwards
#include<stdio.h>
#include<string.h>

int main()
{
    int j,i; int lastWhiteSpace = 0; //there were no white spaces
    char str[100];

    printf("Enter String\n");

    gets(str);

    printf("\nString in Reverse Order\n");

    i=0;
    while(str[i]!='\0')
    {
        if(str[i]==' ')
        {
            for(j=i-1;j>=lastWhiteSpace;j--)  //Loop starts from last char and decrements upto the character after the last white space 
                printf("%c",str[j]);
            printf(" ");
            lastWhiteSpace = i + 1; //the character after this white space 
        }
        i++;
    }

    //later edit
    for(j=i-1;j>=lastWhiteSpace;j--)
        printf("%c",str[j]);
    printf("\n");
}

Answer 3

每次将内循环测试为零时，每次都会打印到字符串的开头。你需要测试直到找到最后的空间。对于内循环

这样的东西

int lastSpace = 0, i = 0, j = 0;
while(str[i] != '\0')
{
if(str[i] == ' ')
{
for(j = i-i; j>= lastSpace; j++)
{
   printf("%c", str[j]);
}
lastSpace = i;
}
i++;
}

Answer 4

无需在单循环中进行双循环。

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

int main()
{
    int j,i, len;
    char str[100];
    clrscr();
    printf("Enter String\n");
    gets(str);
    printf("\nString in Reverse Order\n");
    i = strlen(str) - 1;
    while(i > -1)
    {
    printf("%c",str[i--]);
    }
}

Answer 5

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

int main()
{
    int j,i, len;
    char str[100];
    char temp[20];
    clrscr();
    printf("Enter String\n");
    gets(str);
    printf("\nString in Reverse Order\n");
    i = 0;
    len = 0;
    j = 0;
    while(str[i] != '\0')
    {
        if(str[i] != ' ')
            temp[j++] = str[i];

        if(str[i] == ' ')
        {
            temp[j] = '\0';
            len = strlen(temp);

            while(len > -1)
            {
                printf("%c", temp[len--]);
            }
            printf(" ");
            len = 0;
            j = 0;
        }
    i++;
    }
    temp[j] = '\0';
    len = strlen(temp);
    printf(" ");
    while(len > -1)
    {
        printf("%c",temp[len--]);
    }
}

c程序用于向后打印字符串中的每个单词

5 个答案: