实验五

实验任务一

task1

程序源码

#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;
}

 

程序运行

 

task2

程序源码

#include <stdio.h>

int main() {
    
    int x[2][4] = {{1, 9, 8, 4}, {2, 0, 4, 9}};
    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");
    }
    
    return 0;
}

 

程序运行

 

实验任务二

task1

程序源码

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

int main() {
    
    char s1[] = "Learning makes me happy";
    char s2[] = "Learning makes me sleepy";
    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;
}

 

程序运行

 

问题回答

1.数组s1的大小是24，sizeof计算的是大小包括'0'，strlen计算的是长度
2.不能直接声明一个没有确定大小的数组。
3.交换了

 

task2

程序源码

#include <stdio.h>
#include <string.h>
#define N 80
int main() {
    
    //char *s1 = "Learning makes me happy";
    char *s1;
    s1 = "Learning makes me happy";
    char *s2 = "Learning makes me sleepy";
    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;
}

 

程序运行

 

问题回答

1.指针s1存放的是字符数组的首地址，sizeof计算的一个指针的大小，strlen计算的是长度
2.能
3.交换的是指针，储存单元中的内容没有交换

 

实验任务三

程序源码

#include <stdio.h>
 
void str_cpy(char *target, const char *source);
void str_cat(char *str1, char *str2);

int main() {
    
    char s1[80], s2[20] = "1984";
    
    str_cpy(s1, s2);
    puts(s1);
    
    str_cat(s1, " Animal Farm");
    puts(s1);
    
    return 0;
}

void str_cpy(char *target, const char *source) {
    while (*target++ = *source++);
}

void str_cat(char *str1, char *str2) {
    while (*str1)
        str1++;
    while (*str1++ = *str2++);
}

 

程序运行

 

实验任务四

程序源码

#include <stdio.h>
#define N 80

int func(char *);

int main() {
    
    char str[80];
    while (gets(str) != NULL) {
        if (func(str))
            printf("yes\n");
        else
            printf("no\n");
    }
    
    return 0;
}

int func(char *str) {
    char *begin, *end;
    begin = end = str;
    while (*end)
        end++;
    end--;
    while (begin < end) {
        if (*begin != *end)
            return 0;
        else {
            begin++;
            end--;
        }
    }
    return 1;
}

 

程序运行

 

实验任务五

程序源码

#include <stdio.h>
#define N 80

void func(char *);

int main() {
    char s[N];
    while (scanf("%s", s) != EOF) {
        func(s);
        puts(s);
    }
        
    return 0;
}

void func(char *str)
{
    int i;
    char *p1, *p2, *p;
    
    p1 = str;
    while (*p1 == '*')
        p1++;
        
    p2 = str;
    while (*p2)
        p2++;
    p2--;
    
    while (*p2 == '*')
        p2--;
    p = str;
    
    i = 0;
    while (p < p1) {
        str[i] = *p;
        p++;
        i++;
    }
    while (p <= p2) {
        if (*p != '*') {
            str[i] = *p;
            i++;
        }
        p++;
    }
    while (*p != '\0') {
        str[i] = *p;
        p++;
        i++;
    }
    str[i] = '\0';
}

 

程序运行

 

实验任务六

task1

程序源码

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

void sort(char *name[], int n);

int main() {
    
    char *course[4] = {"C Program",
                        "C++ Object Oriented Program",
                        "Operating System",
                        "Data Structure and Algorithms"};
    int i;
    
    sort(course, 4);
    for (i = 0; i < 4; i++)
        printf("%s\n", course[i]);
        
    return 0;
}

void sort(char *name[], int n) {
    
    int i, j;
    char *tmp;
    
    for (i = 0; i < n - 1; ++i)
        for (j = 0; j < n - 1 - i; ++j)
            if (strcmp(name[j], name[j + 1]) > 0) {
                tmp = name[j];
                name[j] = name[j + 1];
                name[j + 1] = tmp;
            }
}

 

程序运行

 

task2

程序源码

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

void sort(char *name[], int n);

int main() {
    
    char *course[4] = {"C Program",
                        "C++ Object Oriented Program",
                        "Operating System",
                        "Data Structure and Algorithms"};
    int i;
    
    sort(course, 4);
    for (i = 0; i < 4; i++)
        printf("%s\n", course[i]);
        
    return 0;
}

void sort(char *name[], int n) {
    
    int i, j, k;
    char *tmp;
    
    for (i = 0; i < n - 1; i++) {
        k = i;
        for (j = i + 1; j < n; j++)
            if (strcmp(name[j], name[k]) < 0)
                k = j;
            if (k != i) {
                tmp = name[i];
                name[i] = name[k];
                name[k] = tmp;
            }
    }
}
 

 

程序运行

 

问题回答

交换的是内存中字符串的储存位置。

 

实验任务七

程序源码

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

#define N 5

int check_id(char *str);

int main() {
    
    char * pid[N] = {"31010120000721656X",
                    "330106199609203301",
                    "53010220051126571",
                    "510104199211197977",
                    "53010220051126133Y"};
    int i;
    
    for(i = 0;i < N; i++) 
        if(check_id(pid[i]))
            printf("%s\tTrue\n", pid[i]);
        else
            printf("%s\tFalse\n", pid[i]);
    
    return 0;
} 

int check_id(char *str) {
    int len = strlen(str);
    int i;
    
    if(len != 18) return 0;
    
    for(i = 0;i < len; i++) {
        char x = *(str + i);
        if(i == 17) {
            if((x >= '0' && x <= '9') || x =='X') continue ;
            else return 0;
        }
        else {
            if(x >= '0' && x <= '9') continue ;
            else return 0;
        }
    }
    return 1;
}

 

程序运行

 

实验任务八

程序源码

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

#define N 80

void encoder(char *s);
void decoder(char *s);

int main() {
    
    char words[N];
    
    printf("输入英文文本：");
    gets(words);
    
    printf("编码后的英文文本：");
    encoder(words);
    printf("%s\n", words);
    
    printf("对编码后的英文文本解码：");
    decoder(words);
    printf("%s\n", words);
    
    return 0;
}

void encoder(char *s) {
    int i, len;
    
    len = strlen(s);
    
    for(i = 0;i < len; i++) {
        char x;
        x = *(s + i);
        if((x >= 'a' && x <= 'z') || (x >= 'A' && x <= 'Z')) {
            if(x == 'z') *(s + i) = 'a';
            else if(x == 'Z') *(s + i) = 'A';
            else *(s + i) = x + 1;
        }
    }
}

void decoder(char *s) {
    int i, len;
    
    len = strlen(s);
    
    for(i = 0;i < len; i++) {
        char x;
        x = *(s + i);
        if((x >= 'a' && x <= 'z') || (x >= 'A' && x <= 'Z')) {
            if(x == 'a') *(s + i) = 'z';
            else if(x == 'A') *(s + i) = 'Z';
            else *(s + i) = x - 1;
        }
    }
}

 

程序运行