实验六

task1.1

#include<stdio.h>
#define N 4
int main()
{
    int x[N] = { 1,9,8,4 };
    int i;
    int* p;

    for (i = 0; i < N; ++i)
        printf("%d", x[i]);
    printf("\n");

    for (p = x; p < x + N; ++p)
        printf("%d", *p);
    printf("\n");

    p = x;
    for (i = 0; i < N; ++i)
        printf("%d", *(p + i));
    printf("\n");

    p = x;
    for (i = 0; i < N; ++i)
        printf("%d", p[i]);
    printf("\n");

    return 0;
 }

1.2004

2.2001

3.字符与整型变量储存空间不同

task1.2

#include<stdio.h>
#define N 4

int main()
{
    char x[N] = { '1','9','8','4' };
    int i;
    char* p;

    for (i = 0; i < N; ++i)
        printf("%c", x[i]);
    printf("\n");

    for (p = x; p < x + N; ++p)
        printf("%c", *p);
    printf("\n");

    p = x;
    for (i = 0; i < N; ++i)
        printf("%c", *(p + i));
    printf("\n");

    p = x;
    for (i = 0; i < N; ++i)
        printf("%c", p[i]);
    printf("\n");

    return 0;


}

task2.1

#include<stdio.h>
 
int main()
{
    int x[2][4] = { {1,9,8,4},{2,0,2,2} };
    int i, j;
    int* p;
    int(*q)[4];

    for (i = 0; i < 2; ++i)
    {
        for (j = 0; j < 4; ++j)
            printf("%d", x[i][j]);
        printf("\n");
    }

    for (p = &x[0][0], i = 0; p < &x[0][0] + 8; ++p, ++i)
    {
        printf("%d", *p);
        if ((i + 1) % 4 == 0)
            printf("\n");
    }

    for (q = x; q < x + 2; ++q)
    {
        for (j = 0; j < 4; ++j)
            printf("%d", *(*q + j));
        printf("\n");
    }
}

task2.2

#include<stdio.h>

int main()
{
    char x[2][4] = { {'1','9','8','4'},{'2','0','2','2'} };
    int i, j;
    char* p;
    char(*q)[4];

    for (i = 0; i < 2; ++i)
    {
        for (j = 0; j < 4; ++j)
            printf("%c", x[i][j]);
        printf("\n");
    }

    for (p = &x[0][0], i = 0; p < &x[0][0] + 8; ++p, ++i)
    {
        printf("%c", *p);
        if ((i + 1) % 4 == 0)
            printf("\n");
    }

    for (q = x; q < x + 2; ++q)
    {
        for (j = 0; j < 4; ++j)
            printf("%c", *(*q + j));
        printf("\n");
    }

    return 0;
}

1.2004 2017

2.2001 2005

task3.1

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string.h>
#define N 80

int main()
{
    char s1[] = "C,I love u.";
    char s2[] = "C,I hate u.";
    char tmp[N];

    printf("sizeof(s1)vs.strlen(s1):\n");
    printf("sizeof(s1)=%d\n", sizeof(s1));
    printf("strlen(s1)=%d\n", strlen(s1));
    printf("\nbefore swap:\n");
    printf("s1:%s\n", s1);
    printf("s2:%s\n", s2);

    printf("\nswapping...\n");
    strcpy(tmp, s1);
    strcpy(s1, s2);
    strcpy(s2, tmp);

    printf("\nafter swap:\n");
    printf("s1:%s\n", s1);
    printf("s2:%s\n", s2);

    return 0;

}

1.sizeof()计算的是字符数组的大小，strlen()统计的是字符串的长度

2.no

3.yes

task3.2

#include<stdio.h>
#include<string.h>
#define N 80

int main()
{
    char * s1 = "C,I love u.";
    char * s2 = "C,I hate u.";
    char* tmp;

    printf("sizeof(s1)vs.strlen(s1):\n");
    printf("sizeof(s1)=%d\n", sizeof(s1));
    printf("strlen(s1)=%d\n", strlen(s1));

    printf("\nbefore swap:\n");
    printf("s1: %s\n", s1); 
    printf("s2: %s\n", s2);

    printf("\nswapping...\n");
    tmp = s1; 
    s1 = s2; 
    s2 = tmp;

    printf("\nafter swap: \n"); 
    printf("s1: %s\n", s1);
    printf("s2: %s\n", s2); 
    return 0;

}

task4

#include <stdio.h> 
#include <string.h> 
#define N 5 
int check_id(char *str); // 函数声明 
int main()
{
    char* pid[N] = { "31010120000721656X", 
        "330106199609203301", 
        "53010220051126571", 
        "510104199211197977", 
        "53010220051126133Y" };
    int i;

    for (i = 0; i < N; ++i)
        if (check_id(pid[i])) // 函数调用 
            printf("%s\tTrue\n", pid[i]);
        else
            printf("%s\tFalse\n", pid[i]);
    return 0;
}
int check_id(char* str) 
{ 
    int i;
    if (strlen(str) != 18)
        return 0;
    for (i = 0; i < 18; i++)
    {
        if ((str[i] >= '0' && str[i] <= '9') || str[i] == 'x')
            continue;
        else
            return 0;
    }
    return 1;
}

task-6

#include <stdio.h> 
#include <string.h> 
#define N 80 
int is_palindrome(char *s); 
int main() 
{ 
    char str[N]; 
    int flag; 
    printf("Enter a string:\n"); 
    gets_s(str); 
    flag = is_palindrome(str);  
    if (flag) 
        printf("YES\n"); 
    else
        printf("NO\n"); 
    return 0; 
}
int is_palindrome(char* s) 
{ 
    int i, j;
    j = strlen(s);
    for (i = 0; s[i] != '\0'; i++)
    {
        if (s[i] == s[j - i - 1])
            continue;
        else 
            return 0;
    }
    return 1;
}

 task-7

#include <stdio.h> 
#define N 80 
void encoder(char *s); // 函数声明 
void decoder(char *s); // 函数声明 
int main() 
{ 
    char words[N];
    printf("输入英文文本: "); 
    gets_s(words); 
    printf("编码后的英文文本: "); 
    encoder(words); // 函数调用 
    printf("%s\n", words); 
    printf("对编码后的英文文本解码: "); 
    decoder(words); // 函数调用 
    printf("%s\n", words);
    return 0; 
}
void encoder(char* s) 
{ 
    int i, j = 0;
    for (i = 0; s[i] != '\0'; i++)
        j++;
    for (i = 0; i < j; i++)
    {
        if ((s[i] >= 'a' && s[i] < 'z') || (s[i] >= 'A' && s[i] < 'Z'))
            s[i] = s[i] + 1;
        else if ((s[i] == 'z') || (s[i] == 'Z'))
            s[i] = s[i] - 25;
    }
}
void decoder(char* s) 
{ 
    int i, j = 0;
    for (i = 0; s[i] != '\0'; i++)
        j++;
    for (i = 0; i < j; i++)
    {
        if ((s[i] > 'a' && s[i] <= 'z') || (s[i] > 'A' && s[i] <= 'Z'))
            s[i] = s[i] - 1;
        else if ((s[i] == 'a') || (s[i] == 'A'))
            s[i] = s[i] + 25;
    }
}