实验五

实验1

 1 #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 = 0; i < n; ++i)
        if(x[i] < *pmin)
            *pmin = x[i];
        else if(x[i] > *pmax)
            *pmax = x[i];
}

 

作用：历遍数组 找到最大和最小值

pmin指向主函数中min的指针

pmax指向主函数中max的指针

#include <stdio.h>
#define N 5

void input(int x[], int n);
void output(int x[], int n);
int *find_max(int x[], int n);

int main() {
    int a[N];
    int *pmax;

    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");
    pmax = find_max(a, N);

    printf("输出结果:\n");
    printf("max = %d\n", *pmax);

    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");
}

int *find_max(int x[], int n) {
    int max_index = 0;
    int i;

    for(i = 0; i < n; ++i)
        if(x[i] > x[max_index])
            max_index = i;
    
    return &x[max_index];
}

 功能：历遍数组中所有元素 找到最大值并返回其地址

可以 历遍数组后ptr更新为最大元素的地址

实验2

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

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

 

s1大小：80

sizeof（s1）：计算字符组s1所占的总字节数

strlen（s1）：字符串中实际有效的字节数

不能  s1是地址常量，不能被赋值

是  

#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;
}

 

s1：字符串在内存中的首地址

sizeof（s1）：字符指针变量本身的大小

strlen(s1):到‘\0’结束的字符个数

可以 原来是定义指针变量的同时初始化 现在是先定义指针变量 再单独赋值

s1和s2存储的地址值

不会

 

实验3

#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: 使用指针变量ptr1(指向元素)间接访问\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: 使用指针变量ptr2(指向一维数组)间接访问\n");
    for (ptr2 = x; ptr2 < x + 2; ++ptr2) {
        for (j = 0; j < 4; ++j)
            printf("%d ", *(*ptr2 + j));
        printf("\n");
    }

    return 0;
}

 

包含四个int数据类型元素的一维数组的指针

包含四个int数据类型元素的一维数组

 

实验4

#include <stdio.h>
#define N 80

void replace(char *str, char old_char, char new_char); 
int main() {
    char text[N] = "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++;
    }
}

 replace：将所有的old_char 换成 new_char

可以

 

实验5

 

#include <stdio.h>
#define N 80


char *str_trunc(char *str, char x) {
    char *p = str;  
    
    while (*p != '\0') {
        
        if (*p == x) {
            *p = '\0';  
            break;      
        }
        p++;  
    }
    return str;  句）
}

int main() {
    char str[N];
    char ch;
    char *result; 

   
    while (1) {
        printf("输入字符串：");
        scanf("%s", str);  
        printf("输入一个字符：");
        getchar(); 
        ch = getchar();

        printf("截断处理...\n");
        result = str_trunc(str, ch);  

        printf("截断处理后的字符串：%s\n\n", result);

        
        printf("是否继续？(y/n)：");
        ch = getchar();
        getchar();
        if (ch != 'y' && ch != 'Y') {
            break;
        }
    }

    return 0;
}

跳过输入字符的步骤  存放\n

 

实验六

#include <stdio.h>
#include <string.h>
#define N 5

int check_id(char *str);

int main() {
    char *pid[N] = {"31010120000721656X",
                    "3301061996X0203301",
                    "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);
    char *p = str;
    if (len != 18) return 0;
    while (p < str + 17) {
        if (*p < '0' || *p > '9') return 0;
        p++;
    }
    if ((*p >= '0' && *p <= '9') || *p == 'X' || *p == 'x' || *p == 'Y' || *p == 'y')
        return 1;
    else
        return 0;
}

 

实验七

#include <stdio.h>
#define N 80

void encoder(char *str, int n);
void decoder(char *str, int n);

int main() {
    char words[N];
    int n;

    printf("输入英文文本: ");
    gets(words);

    printf("输入n: ");
    scanf("%d", &n);

    printf("编码后的英文文本: ");
    encoder(words, n);
    printf("%s\n", words);

    printf("对编码后的英文文本解码: ");
    decoder(words, n);
    printf("%s\n", words);

    return 0;
}

void encoder(char *str, int n) {
    char *p = str;
    n = n % 26;
    while (*p != '\0') {
        if (*p >= 'a' && *p <= 'z') {
            *p = (*p - 'a' + n) % 26 + 'a';
        } else if (*p >= 'A' && *p <= 'Z') {
            *p = (*p - 'A' + n) % 26 + 'A';
        }
        p++;
    }
}

void decoder(char *str, int n) {
    char *p = str;
    n = n % 26;
    while (*p != '\0') {
        if (*p >= 'a' && *p <= 'z') {
            *p = (*p - 'a' - n + 26) % 26 + 'a';
        } else if (*p >= 'A' && *p <= 'Z') {
            *p = (*p - 'A' - n + 26) % 26 + 'A';
        }
        p++;
    }
}

 

实验八

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

int main(int argc, char *argv[]) {
    int i, j;
    char *tmp;
    if (argc < 2) {
        printf("请输入参数！\n");
        return 1;
    }
    for (i = 1; i < argc - 1; ++i) {
        for (j = i + 1; j < argc; ++j) {
            if (strcmp(argv[i], argv[j]) > 0) {
                tmp = argv[i];
                argv[i] = argv[j];
                argv[j] = tmp;
            }
        }
    }
    for (i = 1; i < argc; ++i) {
        printf("hello, %s\n", argv[i]);
    }
    return 0;
}