实验五
task1_1.c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) //方式一 printf("%d", x[i]); printf("\n"); p = x; for (i = 0; i< N ; ++i)//写法二 printf("%d", *(p + i)); printf("\n"); return 0; }
task1_2.c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; }
task2_1.c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]; // tmp是自己定义的函数名或变量 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; }
问题1：数组s1的大小是24
sizeof(s1)计算的是变量的大小 不受\0影响
strlen(s1)统计的是字符串长度 受\0的影响
问题2：不能 在s1中缺少数组的大小
问题3：内容交换
task2_2.c
#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; // tmp是自己定义的函数名或变量 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; }
问题1：指针变量s1中存放的是字符串
sizeof(s1)计算的是该指针所占的地址空间
strlen(s1)统计的是字符串的长度
问题2：可以替换；task2_2.c是定义char类型的指针变量s1.再给s1赋值字符串；task2_1.c是定义char类型的s1数组。而没有给定数组大小
问题3：交换的是字符串内容；我觉得两个字符串常量在内存存储单元中没有交换
task3.c
#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++) ; }
task4.c
#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; }
task5.c
#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'; }
task6_1.c
#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; } }
task6_2.c
#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; } } }
问题：交换的是指针变量的值。
task7.c
#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 i, flag; if(strlen(str) == 18) { for(i = 0;i < strlen(str); ++i) if(str[i] >= '0'&&str[i] <= '9'||str[i] == 'X') flag = 1; else { flag = 0; break; } if(flag) return 1; else return 0; } else return 0; }
task8.c
#include <stdio.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 = 0; while(s[i] != '\0') { if (s[i] >= 'a'&&s[i] <= 'z'||s[i] >= 'A'&&s[i] <= 'Z') { if (s[i] == 'z' ||s[i] == 'Z') s[i] = s[i] - 31; else s[i] += 1; } i++; } } void decoder(char *s) { int i = 0; while(s[i] != '\0') { if (s[i] >= 'a'&&s[i] <= 'z'||s[i] >= 'A'&&s[i] <= 'Z') { if (s[i] == 'a'||s[i] == 'A') s[i] += 31; else s[i] -= 1; } ++i; } }
