Training4:字符串训练

	1. 题目: 请编写一个C函数,该函数将一个字符串逆序                                                               #include #include void reverse(char str[]) { int len; len = strlen(str); while(len > 0) { len--; printf("%c", str[len]); } printf("\n"); } int main() { char str[20]; printf("enter a string( within 20 bytes):\n"); scanf("%s", str); reverse(str); return 0; }
	2. 题目: 请编写一个C函数,该函数可以实现将一个整数转为任意进制的字符串输出   #include void int_char(int num) { int tmp; int i; int n = 0; int a[1024]; while(num) { a[n++] = num % 10; num /= 10; } for(i = (n - 1); i >= 0; i--) { printf("%d", a[i]); } printf("\n"); } int main() { int num; printf("enter a number:\n"); scanf("%d", &num); int_char(num); return 0; } #include void int_float(char str[], int a[], float b[], int *m, int *n) { *m = 0; *n = 0; int tmp1; float tmp2; int i = 0; while(str[i] != '\0') { while((str[i] <= '9' && str[i] >= '0') || str[i] == '.') { tmp1 = 0; tmp2 = 0; while(str[i] <= '9' && str[i] >= '0') { tmp1 = tmp1 * 10 + str[i] - '0'; i++; } if(str[i] == '.') { tmp2 = tmp1; float k = 0.1; i++; while(str[i] <= '9' && str[i] >= '0') { tmp2 = tmp2 + (str[i] - '0') * k; k *= 0.1; i++; } b[(*n)++] = tmp2; } else { a[(*m)++] = tmp1; } i++; } i++; } } void display(int a[], float b[], int *m, int *n) { int i; printf("the integers is:\n"); for(i = 0; i < *m; i++) { printf("%d", a[i]); } printf("\nthe float is:\n"); for(i = 0; i < *n; i++) { printf("%.3f", b[i]); } printf("\n"); } int main() { int m, n; char str[1024]; int a[1024]; float b[1024]; printf("enter a string:\n"); scanf("%s", str); int_float(str, a, b, &m, &n); display(a, b, &m, &n); return 0; }
	3. 题目: 输入一个字符串,计算字符串中子串出现的次数   #include #include int func(char s[], char str[]) { int i = 0; int j = 0; int num = 0; int count = 0; int len; len = strlen(str); while(s[i] != '\0') { if(str[j] == s[i]) { num++; j++; i++; if((num % len) == 0) { count++; j = 0; } } else if(num != 0) { num = 0; j = 0; } else { i++; } } return count; } int main() { char s[1024]; char str[1024]; printf("enter a string :\n"); scanf("%s", s); printf("enter a short string you want to find:\n"); scanf("%s", str); printf("the string appears %d times\n", func(s, str)); return 0; }
	4. 题目: 编写一个C函数,将”I am from shanghai ”倒置为”shanghai from am I”,及将句子中的单词位置倒置,而不改变单词内部结构.   #include #include void reverse(char a[], int len) { int i, j; char tmp = 0; int n = len - 1; for(i = 0; i < n; i++) { len--; for(j = 0; j < len; j++) { tmp = a[j]; a[j] = a[j + 1]; a[j + 1] = tmp; } } } void re_reverse(char *a) { int n = 0; while(1) { n++; if((*a) == ' ' || (*a) == '\0') { reverse(a - n + 1, n - 1); n = 0; } if((*a) == '\0') { break; } a++; } } int main() { char a[] = "I am from shanghai"; int len; len = strlen(a); reverse(a, len); re_reverse(a); printf("the string after change is:%s\n", a); return 0; }
	5. 题目: 输入一个字符串,同时输入帧头和帧尾(可以是多个字符),将该字符串中合法的帧识别出来. 提示:帧头和帧尾分别是head和tail  字符串”asdheadhauboisoktail”中headhauboisoktail是合法帧   #include #include int flag_h = 0; int flag_t = 0; char * head(char *s, char *h) { int num_h = 0; int len_h = 0; char *tmp = h; len_h = strlen(h); if(s == NULL || h == NULL) { return NULL; } if(strlen(s) < strlen(h)) { return NULL; } while(*s != '\0' && flag_h == 0) { while(*s == *tmp) { num_h++; s++; tmp++; if(num_h == len_h) { flag_h = 1; tmp = s - num_h; break; } } if(num_h != 0 && num_h != len_h) { num_h = 0; tmp = h; s--; } s++; } if(flag_h == 1) { return tmp; } else { printf("illegal string!\n"); } } char * tail(char *s, char *t) { int num_t = 0; int len_t; char *tmp = t; len_t = strlen(t); if(s == NULL || t == NULL) { return NULL; } if(strlen(s) < strlen(t)) { return NULL; } if(flag_h == 1) { while(*s != '\0' && flag_t == 0) { while(*s == *tmp) { s++; tmp++; num_t++; if(num_t == len_t) { flag_t = 1; tmp = s - 1; break; } } if(num_t != 0 && num_t != len_t) { num_t = 0; tmp = t; s--; } s++; } } if(flag_t == 1) { return tmp; } else { printf("illegal string!\n"); return NULL; } } void display(char *start, char *end) { int n; int i; n = end - start + 1; if(n != 0) { for(i = 0; i < n; i++) { printf("%c", *start); start++; } printf("\n"); } else { printf("no data!\n"); } } int main() { char *start = NULL; char *end = NULL; char s[100]; char h[] = "head"; char t[] = "tail"; printf("enter a string(<100):\n"); scanf("%s", s); start = head(s, h); end = tail(s, t); display(start, end); return 0; }