昨天晚上和@buptpatriot讨论函数返回指针(malloc生成的)的问题,提到字符串拼接,做个总结。
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- #include<stdio.h>
- #include<stdlib.h>
- #include<string.h>
- char *join1(char *, char*);
- void join2(char *, char *);
- char *join3(char *, char*);
- int main(void) {
- char a[4] = "abc"; // char *a = "abc"
- char b[4] = "def"; // char *b = "def"
- char *c = join3(a, b);
- printf("Concatenated String is %s\n", c);
- free(c);
- c = NULL;
- return 0;
- }
- /*方法一,不改变字符串a,b, 通过malloc,生成第三个字符串c, 返回局部指针变量*/
- char *join1(char *a, char *b) {
- char *c = (char *) malloc(strlen(a) + strlen(b) + 1); //局部变量,用malloc申请内存
- if (c == NULL) exit (1);
- char *tempc = c; //把首地址存下来
- while (*a != ‘\0‘) {
- *c++ = *a++;
- }
- while ((*c++ = *b++) != ‘\0‘) {
- ;
- }
- //注意,此时指针c已经指向拼接之后的字符串的结尾‘\0‘ !
- return tempc;//返回值是局部malloc申请的指针变量,需在函数调用结束后free之
- }
- /*方法二,直接改掉字符串a,*/
- void join2(char *a, char *b) {
- //注意,如果在main函数里a,b定义的是字符串常量(如下):
- //char *a = "abc";
- //char *b = "def";
- //那么join2是行不通的。
- //必须这样定义:
- //char a[4] = "abc";
- //char b[4] = "def";
- while (*a != ‘\0‘) {
- a++;
- }
- while ((*a++ = *b++) != ‘\0‘) {
- ;
- }
- }
- /*方法三,调用C库函数,*/
- char* join3(char *s1, char *s2)
- {
- char *result = malloc(strlen(s1)+strlen(s2)+1);//+1 for the zero-terminator
- //in real code you would check for errors in malloc here
- if (result == NULL) exit (1);
- strcpy(result, s1);
- strcat(result, s2);
- return result;
- }
时间: 2024-10-25 17:21:45