经典编程900例（c语言）（第十二篇）

例134：删除链表元素

#include <stdio.h> #include <malloc.h> int main(int argc, char const *argv[]) { int i; // 定义链表节点结构 struct ListEntry { int number; struct ListEntry *next; } start, *node, *previous; start.next = NULL; // 初始化链表 node = &start; for (i = 1; i <= 10; i++) { node->next = (struct ListEntry *) malloc(sizeof(struct ListEntry)); node = node->next; node->number = i; node->next = NULL; } // 打印链表 node = start.next; while (node) { printf("%d ", node->number); // 1 2 3 4 5 6 7 8 9 10 node = node->next; } printf("\n"); // 删除数字5 node = start.next; previous = &start; while (node) if (node->number == 5) { // 前一个节点的next指向删除节点的下一个节点 previous->next = node->next; free(node); break; } else { // 指向下一个节点，继续遍历 node = node->next; previous = previous->next; } // 打印链表 node = start.next; while (node) { printf("%d ", node->number); // 1 2 3 4 6 7 8 9 10 node = node->next; } return 0; }

例135：删除双链表的元素

#include <stdio.h> #include <malloc.h> int main(int argc, char const *argv[]) { int i, found; // 定义双向链表节点结构 struct ListEntry { int number; struct ListEntry *next; struct ListEntry *previous; } start, *node; start.next = NULL; start.previous = NULL; // 初始化链表 node = &start; for (i = 1; i <= 10; i++) { node->next = (struct ListEntry *) malloc(sizeof(struct ListEntry)); node->next->previous = node; node = node->next; node->number = i; node->next = NULL; } // 删除数字7 node = start.next; found = 0; do { if (node->number == 7) { found = 1; // 删除元素前一个节点的next指向下一个节点 node->previous->next = node->next; // 删除元素的下一个节点的previous指向前一个节点 node->next->previous = node->previous; free(node); } else node = node->next; } while ((node) && (!found)); // 打印链表 node = start.next; do { printf("%d ", node->number); node = node->next; } while (node); return 0; }

例136：枚举的定义使用1

#include <stdio.h> int main(int argc, char const *argv[]) { // 定义枚举类型weekdays并定义初始化枚举变量 enum weekdays { Monday = 10, Tuesday = 20, Wednesday = 30, Thursday = 40, Friday = 50 }; printf("%d %d %d %d %d\n", Monday, Tuesday, Wednesday, Thursday, Friday); // 10 20 30 40 50 return 0; }

例137：枚举的定义使用2

#include <stdio.h> int main(int argc, char const *argv[]) { // // 定义枚举类型weekdays并定义枚举变量（默认值初始化） enum weekdays { Monday, Tuesday, Wednesday, Thursday, Friday}; printf("%d %d %d %d %d\n", Monday, Tuesday, Wednesday, Thursday, Friday); // 0 1 2 3 4 return 0; }

例138：顺序打印指定目录下的文件夹名

#include <stdio.h> #include <dirent.h> #include <malloc.h> #include <string.h> #include <stdlib.h> int main(int argc, char const *argv[]) { DIR *directory_pointer; struct dirent *entry; // 定义文件链表结构 struct FileList { char filename[64]; struct FileList *next; } start, *node, *previous, *new; // 打开文件夹错误 if ((directory_pointer = opendir(argv[1])) == NULL) printf("Error opening %s\n", argv[1]); else { start.next = NULL; while (entry = readdir(directory_pointer)) { previous = &start; node = start.next; // 排序 while ((node) && (strcmp(entry, node->filename) > 0)) { node = node->next; previous = previous->next; } new = (struct FileList *) malloc(sizeof(struct FileList)); if (new == NULL) { printf("Insufficient memory to store list\n"); exit(1); } new->next = node; previous->next = new; strcpy(new->filename, entry); } closedir(directory_pointer); // 打印文件夹链表 node = start.next; while (node) { printf("%s\n", node->filename); node = node->next; } } return 0; }

例139：创建子进程1

#include <process.h> #include <stdio.h> int main(int argc, char const *argv[]) { printf("About to call child process\n\n"); spawnl(P_WAIT, "CHILD.EXE", "CHILD.EXE", "AAA", "BBB", "CCC", NULL); printf("\n\nBack from child process\n"); return 0; }

例140：创建子进程2

#include <process.h> #include <stdio.h> int main(int argc, char const *argv[]) { char *env[] = {"FILE=SPAWNLXX.C", "LANGUAGE=C", "OS=DOS", NULL}; spawnle(P_WAIT, "CHILD.EXE", "CHILD.EXE", "Using-spawnle", "BBB", NULL, env); spawnlp(P_WAIT, "CHILD.EXE", "CHILD.EXE", "Using-spawnlp", "BBB", NULL); spawnlpe(P_WAIT, "CHILD.EXE", "CHILD.EXE", "Using-spawnlpe", "BBB", NULL, env); return 0; }

例141：创建子进程3

#include <stdio.h> #include <process.h> int main(int argc, char const *argv[]) { char *env[] = {"FILENAME=SPAWNVXX.C", "OS=DOS", "ROUTINES=SPAWNVXX", NULL }; char *argv[] = { "CHILD.EXE", "AAA", "BBB", NULL }; spawnv(P_WAIT, "CHILD.EXE", argv); spawnve(P_WAIT, "CHILD.EXE", argv, env); spawnvp(P_WAIT, "CHILD.EXE", argv); spawnvpe(P_WAIT, "CHILD.EXE", argv, env); return 0; }

例142：查看当前路径文件目录

#include <stdio.h> #include <stdlib.h> int main(int argc, char const *argv[]) { if (system("DIR")) printf("Error invoking DIR\n"); return 0; }

例143：想想下面代码正确吗？

#include <stdio.h> int value; int main(int argc, char const *argv[]) { printf("%d\n", value); return 0; } int value = 1001;

例144：枚举遍历

#include <stdio.h> int main(int argc, char const *argv[]) { enum { Monday, Tuesday, Wednesday, Thursday, Friday } day; // 遍历 for (day = Monday; day <= Friday; day++) if (day == Monday) printf("No fun---meetings all day Monday\n"); else if (day == Tuesday) printf("No fun---do Monday's work today\n"); else if (day == Wednesday) printf("Hump day..."); else if (day == Thursday) printf("Schedule meetings for next Monday\n"); else printf("Meet everyone at happy hour!\n"); return 0; }