实验5
task1_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]; }
Q1:找出最大值与最小值
Q2：指向x[0]
task1_2
#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_s("%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]; }
Q1:返回5个数据中最大值的地址
Q2：可以
task 2_1
#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; }
Q1:数组s1大小为80个字节；sizeof计算的是s1所占字节数；strlen表示的是实际字符数
Q2：不可以。字符串不可以赋值给数组
Q3：是互相交换
task 2_2
#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; }
Q1:指针s1存放第一个字符的地址；sizeof计算s1指向地址所占用的字节数；strlen统计实际字符个数
Q2：可以。task2_1中是将字符串赋值给数组地址；task2_2中是将指针变量s1指向字符串的第一个字符的地址
Q3：交换的是地址；内存没有交换
task 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; }
Q1：指针ptr指向有4个int类型数据的一维数组
Q2：ptr是含有4个指针变量的数组
task 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++; } }
Q1：将文本中的“i”全部替换成“*”
Q2：可以
task 5
#include <stdio.h> #define N 80 char *str_trunc(char *str, char x); int main() { char str[N]; char ch; while (printf("输入字符串："), gets(str) != NULL) { 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\n", str); getchar(); } return 0; } char *str_trunc(char *str, char x) { int i; for (i = 0;i < N;i++) { if (str[i] == x) { str[i] = '\0'; break; } } return str; }
Q:删去getchar后多组输入失败，getchar（）的作用是读取回车键
task 6
#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\tTure\n", pid[i]); else printf("%s\tFalse\n", pid[i]); return 0; } int check_id(char *str) { int len,i; len = strlen(str); if (len != 18) return 0; for (i = 0;i < 17;i++) { if (str[i] < '0' || str[i]>"9") return 0; } if ((str[17] > '0' && str[17] < '9') || str[17] == 'X') return 1; else return 0; }
task 7
#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_s("%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) { while (*str != '\0') { if (*str >= 'a' && *str <= 'z') * str = (*str - 'a' + n) % 26 + 'a'; if (*str >= 'A' && *str <= 'Z') * str = (*str - 'A' + n) % 26 + 'A'; str++; } } void decoder(char* str, int n) { while (*str != '\0') { if (*str >= 'a' && *str <= 'z') *str = (*str - 'a' -n+26) % 26 + 'a'; if (*str >= 'A' && *str <= 'Z') *str = (*str - 'A'-n+26) % 26 + 'A'; str++; } }
task 8
#include <stdio.h> #include <stdlib.h> #include <string.h> int compare(const void* a, const void* b) { return strcmp(*(const char**)a, *(const char**)b); } int main(int argc, char* argv[]) { if (argc < 2) { printf("请输入姓名列表\n"); return 1; } qsort(argv + 1, argc - 1, sizeof(char*), compare); for (int i = 1; i < argc; ++i) { printf("hello, %s\n", argv[i]); } return 0; }
