实验5
实验任务1
程序源码1.1
#include <stdio.h> #define N 4 int main() { int x[N] = {1, 9, 8, 4}; int i; int *p; // 方式1:通过数组名和下标遍历输出数组元素 for (i = 0; i < N; ++i) printf("%d", x[i]); printf("\n"); // 方式2:通过指针变量遍历输出数组元素 (写法1) for (p = x; p < x + N; ++p) printf("%d", *p); printf("\n"); // 方式2:通过指针变量遍历输出数组元素(写法2) p = x; for (i = 0; i < N; ++i) printf("%d", *(p + i)); printf("\n"); // 方式2:通过指针变量遍历输出数组元素(写法3) p = x; for (i = 0; i < N; ++i) printf("%d", p[i]); printf("\n"); return 0; }
运行结果1.1
程序源码1.2
#include <stdio.h> int main() { int x[2][4] = {{1, 9, 8, 4}, {2, 0, 4, 9}}; int i, j; int *p; // 指针变量,存放int类型数据的地址 int(*q)[4]; // 指针变量,指向包含4个int型元素的一维数组 // 使用数组名、下标访问二维数组元素 for (i = 0; i < 2; ++i) { for (j = 0; j < 4; ++j) printf("%d", x[i][j]); printf("\n"); } // 使用指针变量p间接访问二维数组元素 for (p = &x[0][0], i = 0; p < &x[0][0] + 8; ++p, ++i) { printf("%d", *p); if ((i + 1) % 4 == 0) printf("\n"); } // 使用指针变量q间接访问二维数组元素 for (q = x; q < x + 2; ++q) { for (j = 0; j < 4; ++j) printf("%d", *(*q + j)); printf("\n"); } return 0; }
运行结果1.2
实验任务2
程序源码2.1
#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; }
运行结果2.1
问题1:数组s1的大小为24个字节;sizeof(s1)计算的是数组大小,strlen(s1)计算的是字符数组长度
问题2:不可以,数组s1的长度未知
问题3:内容交换了
程序源码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; }
运行结果2.2
问题1:s1中存放的是字符串,sizeof(s1)计算的是字符串所占用的空间,strlen(s1)计算的是字符串的长度
问题2:可以,2.1中的写法是先定义一个空的数组s1,在s1中存放字符串。2.2中的写法表示定义一个指针变量s1,s1指向数组
问题3:交换的是指针的指向,s1和s2的储存单元没有改变
实验任务3
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++); }
运行结果
实验任务4
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; }
运行结果
实验任务5
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'; }
运行结果
实验任务6
程序源码(冒泡排序)
#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; } }
运行结果
程序源码(选择排序)
"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; } } }
运行结果
两种算法交换的是指针变量的值
实验任务7
#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){ char *p=str; if(strlen(str)!=18){ return 0; } while(*p!='\0'){ if((*p>'9'||*p<'0')&&*p!='X'){ return 0;} p++;} return 1; }
运行结果
实验任务8
程序源码
#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) { char *p=s; while(*p!='\0'){ if(*p>='a'&&*p<='z') *p=*p+1; else if(*p=='a') *p='z'; else if(*p>='A'&&*p<='Z') *p=*p+1; else if(*p=='A') *p=='Z'; p++; } } void decoder(char *s) { char *p=s; while(*p!='\0'){ if(*p>='a'&&*p<='z') *p=*p-1; else if(*p=='z') *p='a'; else if(*p>='A'&&*p<='Z') *p=*p-1; else if(*p=='Z') *p=='A'; p++; } }
运行结果