C语言常见字符串面试题.pdf

C语言常见字符串面试题 1. 字符串库函数的内部实现 memset库函数的实现 /* * memset - Fill a region of memory with the given value * s: Pointer to the start of the area. * c: The byte to fill the area with * count: The size of the area. */ void *memset(void *s, int c, size_t count) char *xs = s; while (count-) *xs+ = c; return s; memcpy库函数的实现 /* * memcpy - Copy one area of memory to another * dest: Where to copy to * src: Where to copy from * count: The size of the area. */ void *memcpy(void *dest, const void *src, size_t count) char *tmp = dest; const char *s = src; while (count-) *tmp+ = *s+; return dest; memmove库函数的实现 /* * memmove - Copy one area of memory to another * dest: Where to copy to * src: Where to copy from * count: The size of the area. * Unlike memcpy(), memmove() copes with overlapping areas. */ void *memmove(void *dest, const void *src, size_t count) char *tmp; const char *s; if (dest = l2) l1-; if (!memcmp(s1, s2, l2) return (char *)s1; s1+; return NULL; 常见字符串面试题 1)写出在母串中查找子串出现次数的代码. int count1(char* str, char* s) char* s1; char* s2; int count = 0; while(*str!=/0) s1 = str; s2 = s; while(*s2 = *s1 s1+; if(*s2 = /0) count+; str+; return count; 2）查找第一个匹配子串位置,如果返回的是s1长度len1表示没有找到 size_t find(char* s1,char* s2) size_t i=0; size_t len1 = strlen(s1) size_t len2 = strlen(s2); if(len1-len2 #include #include char *commanstring(char shortstring, char longstring) int i, j; char *substring=malloc(256); if(strstr(longstring, shortstring)!=NULL)/如果，那么返回shortst ring return shortstring; for(i=strlen(shortstring)-1;i0; i-) /否则，开始循环计算 for(j=0; jstrlen(str2) /将短的字符串放前面 comman=commanstring(str2, str1); else comman=commanstring(str1, str2); printf(“the longest comman string is: %s/n“, comman); 6) 判断一个字符串是不是回文 int IsReverseStr(char *str) int i,j; int found=1; if(str=NULL) return -1; char* p