实验5C语言指针应用编程

 #include <stdio.h>
 #define N 5
 void input(int x[], int n);
 void output(int x[], int n);
 void find_min_max(int x[], int n, int *pmin, int *pmax);
 int main() {
 int a[N];
 int min, max;
 printf("录入%d个数据:\n", N);
 input(a, N);
 printf("数据是: \n");
 output(a, N);
 printf("数据处理...\n");
 find_min_max(a, N, &min, &max);
 printf("输出结果:\n");
 printf("min = %d, max = %d\n", min, max);
 return 0;
 }
 void input(int x[], int n) {
 int i;
 for(i = 0; i < n; ++i)
 scanf("%d", &x[i]);
 }
 void output(int x[], int n) {
 int i;
 for(i = 0; i < n; ++i)
 printf("%d ", x[i]);
 printf("\n");
 }
 void find_min_max(int x[], int n, int *pmin, int *pmax) {
 int i;
 *pmin = *pmax = x[0];
 for(i = 1; i < n; ++i)
 if(x[i] < *pmin)
 *pmin = x[i];
 else if(x[i] > *pmax)
 *pmax = x[i];
 }

#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;
 }

不可以替换第六行，会因未声明数组大小而不能编译。

#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;
    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;
 }

可以替换，指针节省空间且不需要提前申请

#include <stdio.h>
 #include <stdio.h>
 int main() {
    int x[2][4] = {{1, 9, 8, 4}, {2, 0, 4, 9}};
    int i, j;
    int *ptr1;     
    int(*ptr2)[4]; 
    printf("输出1: 使用数组名、下标直接访问二维数组元素\n");
    for (i = 0; i < 2; ++i) {
        for (j = 0; j < 4; ++j)
            printf("%d ", x[i][j]);
        printf("\n");
    }
    printf("\n输出2: 使用指向元素的指针变量ptr1间接访问二维数组元素\n");
    for (ptr1 = &x[0][0], i = 0; ptr1 < &x[0][0] + 8; ++ptr1, ++i) {
        printf("%d ", *ptr1);
        if ((i + 1) % 4 == 0)
            printf("\n");
    }
    printf("\n输出3: 使用指向一维数组的指针变量q间接访问二维数组元素\n");
    for (ptr2 = x; ptr2 < x + 2; ++ptr2) {
        for (j = 0; j < 4; ++j)
            printf("%d ", *(*ptr2 + j));
        printf("\n");
    }
    return 0;
 }

#include <stdio.h>
 #define N 80
 void replace(char *str, char old_char, char new_char); // 函数声明
int main() {
    char text[N] = "c programming is difficult or not, it is a question.";
    printf("原始文本: \n");
    printf("%s\n", text);
    replace(text, 'i', '*');
    printf("处理后文本: \n");
    printf("%s\n", text);
     return 0;
 }
void replace(char *str, char old_char, char new_char) {
    int i;
    while(*str) {
        if(*str == old_char)
            *str = new_char;
        str++;
    }
 }

#include <stdio.h>
 #define N 80
 void str_trunc(char *str, char x);  
int main() {
    char str[N];
    char ch;
    printf("输入字符串: ");
    gets(str);
    printf("输入一个字符: ");
    ch = getchar();
    printf("截断处理...\n");
    str_trunc(str, ch);
    printf("截断处理后的字符串: %s\n", str);
 }
 void str_trunc(char *str, char x) {
    while(*str) {
        if(*str == x)
           *str='\0';     
        str++;   
    }
    str=str-1;  
 }

#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])) // 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 t,i;
        t=strlen(str);
        if(t!=18)
         return 0;
        if((*(str+17)>='0'&&*(str+17)<='9')||*(str+17)=='X')
          for(i=0;i<17;++i,++str)
           if(*(str)>='0'&&*(str)<='9')
           return 1;
           else
           return 0;
          else
          return 0;
}

#include <stdio.h>
#define N 80
void encoder(char *str); 
void decoder(char *str); 
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); // 函数调用
    printf("%s\n", words);

    return 0;
}
void encoder(char *str) {
     for(;*str!='\0';++str)
       {
       if((*str>='A'&&*str<'Z')||(*str>='a'&&*str<'z'))
         *str=(*str)+1;
       else if (*str=='Z')
         *str='A';
       else if(*str=='z')
         *str='a';
       }
}
void decoder(char *str) {
    for(;*str!='\0';++str)
    {
    if((*str>='A'&&*str<'Z')||(*str>='a'&&*str<'z'))
      *str=(*str)-1;
    else if(*str=='A')
      *str='Z';
    else if(*str=='a')
      *str='z';
    }
}