C程序 - 输出显示在下一行，不使用换行符

Question

在此代码中输入所有用户输入后，当被要求代码必须为其输出时。

这是下面给出的代码的一部分，它打印输出但在打印city_1[i].city的输出后，更新的输出打印在换行符上。

在printf声明中，"\n"之后我没有使用"%s"。

for (i = 0; i <= k - 1; i++) {
    printf("   %s      %d      %f%", city_1[i].city, city_1[i].p, city_1[i].l);
    //printf("\n");
}   

我正在使用 Visual Studio 2015 来调试我的代码。

任何人都可以在这个问题上帮助解释我吗？

以下是我的代码：

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

//GLOBAL-VARIABLE DECLARTION
#define MAX 1000

//GLOBAL-STRUCTURES DECLARATION
struct census {
    char city[MAX];
    long int p;
    float l;
};

//GLOBAL-STRUCTURE-VARIABLE DECLARATION
struct census cen[MAX] = { 0 };

//USER-DEFINED FUNCTION
struct census sortm_city(struct census city_1[]);
struct census sortm_population(struct census popu[]);
struct census sortm_literacy(struct census lite[]);
void header();

void header() {
    printf("*-*-*-*-*CENSUS_INFO*-*-*-*-*");
    printf("\n\n");
}

//PROGRAM STARTS HERE
main() {    
    //VARIABLE-DECLARATION
    int i = 0, j = 0, n = 0;
    char line[MAX] = { 0 };
    char o = { 0 };

    //FUNCTION CALL-OUT
    header();

    printf("Enter No. of City : ");
    fgets(line, sizeof(line), stdin);
    sscanf_s(line, "%d", &j);

    printf("\n\n");

    printf("Enter Name of City, Population and Literacy level");
    printf("\n\n");

    for (i = 0; i <= j - 1; i++) {
        printf("City No. %d - Info :", i + 1);
        printf("\n\n");

        printf("City Name : ");
        fgets(cen[i].city, MAX, stdin);
        printf("\n");

        printf("Population : ");
        fgets(line, sizeof(line), stdin);
        sscanf_s(line, "%d", &cen[i].p);
        printf("\n");

        printf("Literacy : ");
        fgets(line, sizeof(line), stdin);
        sscanf_s(line, "%f", &cen[i].l);
        printf("\n");

        printf("_____________________________________");
        printf("\n\n");
    }

    printf("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* ");
    printf("Census Information");
    printf(" *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
    printf("\n\n");

    for (i = 0; i <= j - 1; i++) {
        printf("City No. %d - Info :", i + 1);
        printf("\n\n");

        printf("City Name : %s", cen[i].city);
        printf("\n");

        printf("Population : %d", cen[i].p);
        printf("\n");

        printf("Literacy : %0.2f", cen[i].l);
        printf("\n");

        printf("_____________________________________");
        printf("\n\n");
    }

    printf("Enter one option from the following : \n\n");
    printf("(a) To Sort the List Alphabetically. \n");
    printf("(b) To Sort the List based on Literacy Level. \n");
    printf("(c) To Sort the List based on Population. \n\n");
    printf("Please type a proper option. \n");

    n = 0;

    while (n == 0) {
        scanf_s(" %c", &o);

        switch (o) {
          case 'a':
            sortm_city(cen, j);
            n = 1;
            break;

          case 'b':
            sortm_population(cen);
            n = 1;
            break;

          case 'c':
            sortm_literacy(cen);
            n = 1;
            break;

          default:
            printf("Option INVALID \n");
            printf("Please type a proper option. \n");
            n = 0;
            break;
        }
    }

    //TERMINAL-PAUSE
    system("pause");
}

struct census sortm_city(struct census city_1[], int k) {
    int i = 0, j = 0;
    //FOR TRANSFERRING
    float b = 0;
    int s = 0;
    char line_0[MAX] = { 0 };

    for (i = 1; i <= k - 1; i++) {
        for (j = 1; j <= k - 1; j++) {
            if (strcmp(city_1[j - 1].city, city_1[j].city) > 0) {
                //SORTING THE LIST ALPHABETICALLY.
                strcpy(line_0, city_1[j - 1].city);
                strcpy(city_1[j - 1].city, city_1[j].city);
                strcpy(city_1[j].city, line_0);

                //COPYING POPULATION AND LITERACY TO RIGHT PLACE.

                //POPULATION :
                s = city_1[j - 1].p;
                city_1[j - 1].p = city_1[j].p;
                city_1[j].p = s;

                //LITERACY : 
                b = city_1[j - 1].l;
                city_1[j - 1].l = city_1[j].l;
                city_1[j].l = b;
            }
        }
    }

    printf("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* ");
    printf("Sorted list in Alphabetical Order");
    printf(" *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
    printf("\n\n");

    printf("___________________________________________________\n");
    printf("|   *City Name*   |   Population   |   Literacy   | \n");

    for (i = 0; i <= k - 1; i++) {
        printf("   %s      %d      %f%", city_1[i].city, city_1[i].p, city_1[i].l);
        //printf("\n");
    }
}

struct census sortm_population(struct census popu[]) {
    printf("-------");
}

struct census sortm_literacy(struct census lite[]) {
    printf("-------");
}

Answer 1

fgets包含用户在返回的字符串中键入的\n字符。因此，当您打印该字符串时，您将获得一个新行。

Answer 2

问题来自于fgets()在从流中读取的行末尾留下的换行符。如果缓冲区太短或者文件中的最后一行没有以行终止符结束，则缓冲区不会在最终\n之前以\0结束，在所有其他情况下，它将

删除换行符的简单方法是：

line[strcspn(line, "\n")] = '\0';

如果找到\n，则会覆盖\0，否则会用\0覆盖fgets()。

请注意，您应该测试NULL的返回值，如果它无法读取文件末尾的行，则返回for。

另请注意，以这种方式编写for (i = 0; i < j; i++) { ... } 循环更简单，更惯用：

0

索引j将被包含在内，索引qsort将不会出现，这与您的语法相同，但更简单易读。

您还可以使用main()使用3种不同的比较函数对表格进行排序。

另请注意，您对int main(void)的定义已过时且不适用于C99及更高版本的C标准。您应该写int main(int argc, char *argv[])或p。

以下是问题列表：

• 您将人口普查成员long int定义为%d，但使用sscanf通过printf阅读并使用%ld打印，正确格式为{{ 1}}。
• 您将sortm_xxx函数定义为返回struct census，这是不正确的，sortm_city确实不返回任何内容，它们应定义为void。
• header应声明并定义为void header(void)
• main应定义为int main(void)
• 您使用scanf_s和sscanf_s。 Visual Studio可能推荐使用这些函数，但scanf和sscanf并非总能在其他系统上使用这些函数，并且可以安全地使用这些函数并采取一些预防措施，尤其是%s和{%[ {1}}格式，无论如何你都不会在这里使用。
• fgets将\n留在行尾。您应该检查retuen值以检测文件的过早结束并去除\n。我定义了一个实用程序函数xgets()。 strcspn()返回其字符串参数中的字符数，这些字符不在作为第二个字符串参数给出的列表中。
• 打印代码使用%f作为识字级别，产生6个小数位（默认值），您应该使用%7.2f获得2个小数位并对齐列内容。
• 您必须使用%%打印% printf字符。
• 我在printf格式字符串中添加了一些对齐参数以对齐输出，假设使用固定宽度字体："| %-15s | %10ld | %7.2f%% |"。 %-15s将城市名称填充为15个字符，并在城市名称之后填充空格，%10ld将人口填充为10个字符，空格之前人口数字。 %7.2f生成2个小数位，并且在.之前的识字数字最多为7个字符之前用空格填充。
• 我使用qsort并为3个排序选项定义了3个比较函数。
• 我将用于打印人口普查数据的代码移动到单独的功能中。最好是以这种方式分解代码以编写更少的代码，并避免在以后修复错误时出现不一致。

以下是更正后的简化版本：

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

//GLOBAL-VARIABLE DECLARTION
#define MAX 1000

//GLOBAL-STRUCTURES DECLARATION
struct census {
    char city[MAX];
    long int p;
    float l;
};

//GLOBAL-STRUCTURE-VARIABLE DECLARATION
struct census cen[MAX] = { 0 };

//USER-DEFINED FUNCTION
void header(void);
void sortm_city(struct census cp[], int n);
void sortm_population(struct census cp[], int n);
void sortm_literacy(struct census cp[], int n);
void print_census(struct census cp[], int k, const char *legend);

void header(void) {
    printf("*-*-*-*-*CENSUS_INFO*-*-*-*-*");
    printf("\n\n");
}

char *xgets(char *dest, int size, FILE *fp) {
    /* read a line from the user */
    if (!fgets(dest, size, fp)) {
        /* read failed, end of file detected */
        printf("Premature end of file\n");
        exit(1);
    }
    /* strip the \n if present */
    dest[strcspn(dest, "\n")] = '\0';
    return dest;
}

//PROGRAM STARTS HERE
int main(void) {
    //VARIABLE-DECLARATION
    int i = 0, j = 0, n = 0;
    char line[MAX] = { 0 };
    char o = { 0 };

    //FUNCTION CALL-OUT
    header();

    printf("Enter No. of City : ");
    xgets(line, sizeof(line), stdin);
    if (sscanf(line, "%d", &j) != 1)
        return 1;

    printf("\n\n");
    printf("Enter Name of City, Population and Literacy level");
    printf("\n\n");

    for (i = 0; i < j; i++) {
        printf("City No. %d - Info :", i + 1);
        printf("\n\n");

        printf("City Name : ");
        xgets(cen[i].city, MAX, stdin);
        printf("\n");

        printf("Population : ");
        xgets(line, sizeof(line), stdin);
        sscanf(line, "%ld", &cen[i].p);
        printf("\n");

        printf("Literacy : ");
        xgets(line, sizeof(line), stdin);
        sscanf(line, "%f", &cen[i].l);
        printf("\n");

        printf("_____________________________________");
        printf("\n\n");
    }

    printf("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* ");
    printf("Census Information");
    printf(" *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
    printf("\n\n");

    for (i = 0; i < j; i++) {
        printf("City No. %d - Info :", i + 1);
        printf("\n\n");

        printf("City Name : %s", cen[i].city);
        printf("\n");

        printf("Population : %ld", cen[i].p);
        printf("\n");

        printf("Literacy : %0.2f", cen[i].l);
        printf("\n");

        printf("_____________________________________");
        printf("\n\n");
    }

    printf("Enter one option from the following : \n\n");
    printf("(a) To Sort the List Alphabetically. \n");
    printf("(b) To Sort the List based on Literacy Level. \n");
    printf("(c) To Sort the List based on Population. \n\n");
    printf("Please type a proper option. \n");

    n = 0;
    while (n == 0) {
        scanf(" %c", &o);

        switch (o) {
        case 'a':
            sortm_city(cen, j);
            n = 1;
            break;

        case 'b':
            sortm_population(cen, j);
            n = 1;
            break;

        case 'c':
            sortm_literacy(cen, j);
            n = 1;
            break;

        default:
            printf("Option INVALID \n");
            printf("Please type a proper option. \n");
            n = 0;
            break;
        }
    }

    //TERMINAL-PAUSE
    system("pause");
}

void print_census(struct census cp[], int k, const char *legend) {
    int i;

    printf("*-*-*-*-*-*-*-*- %s *-*-*-*-*-*-*-*-*-*", legend);
    printf("\n\n");
    printf("___________________________________________________\n");
    printf("|    City Name    |   Population   |   Literacy   |\n");
    printf("___________________________________________________\n");

    for (i = 0; i < k; i++) {
        printf("| %-15s |   %10ld   |   %7.2f%%   |", cp[i].city, cp[i].p, cp[i].l);
        printf("\n");
    }
    printf("___________________________________________________\n");
    printf("\n\n");
}

int compare_census_city(const void *a, const void *b) {
    const struct census *ca = a;
    const struct census *cb = b;
    return strcmp(ca->city, cb->city);
}

int compare_census_population(const void *a, const void *b) {
    const struct census *ca = a;
    const struct census *cb = b;
    if (ca->p > cb->p)
        return -1;
    if (ca->p < cb->p)
        return 1;
    return 0;
}

int compare_census_literacy(const void *a, const void *b) {
    const struct census *ca = a;
    const struct census *cb = b;
    if (ca->l > cb->l)
        return -1;
    if (ca->l < cb->l)
        return 1;
    return 0;
}

void sortm_city(struct census cp[], int n) {
    qsort(cp, n, sizeof(struct census), compare_census_city);
    print_census(cp, n, "Sorted list in Alphabetical Order");
}

void sortm_population(struct census cp[], int n) {
    qsort(cp, n, sizeof(struct census), compare_census_population);
    print_census(cp, n, "Sorted list by decreasing Popupation");
}

void sortm_literacy(struct census cp[], int n) {
    qsort(cp, n, sizeof(struct census), compare_census_literacy);
    print_census(cp, n, "Sorted list in decreasing Literacy level");
}