注：编码工具是CLion+Cygwin64
目录
字符串的两种定义方式
自定义获取字符串长度方法
方式一：
方式二：
字符串转数字
比较
查找和包含
拷贝和拼接
大小写转换
字符串的两种定义方式
方式一：字符数组
此种方式需要在最后一个元素后面添加' '，C语言的字符串以' '结尾。
方式二：字符指针
此种方式隐式添加' '。
#includeint main(){ char str[7] = {'S', 't', 'r', 'i', 'n', 'g'}; printf("str = %sn", str); char str3[] = {'C', 'o', 'l', 'd', ' '}; printf("str3 = %sn", str3); str3[0] = 'F'; printf("str3 = %sn", str3); char * str2 = "Here I Am"; printf("str2 = %sn", str2); // str2[2] = 'e'; // 不能如此操作 // printf("str2 = %sn", str2); return 0; }
输出：
str = String str3 = Cold str3 = Fold str2 = Here I Am
自定义获取字符串长度方法
方式一：
#include
int len(char *str) {
char *tmp = str;
int count = 0;
while (*tmp) {
count++;
tmp++;
}
return count;
}
int main() {
char *str = "Better Babe";
int length = len(str);
printf("str's length is %dn", length);
return 0;
}
#includeint len(char *str) { char *tmp = str; int count = 0; while (*tmp) { count++; tmp++; } return count; } int main() { char *str = "Better Babe"; int length = len(str); printf("str's length is %dn", length); return 0; }
输出：
str's length is 11
方式二：
#include
void len(int * length, char *str) {
char *tmp = str;
int count = 0;
while (*tmp) {
count++;
tmp++;
}
*length = count;
}
int main() {
char str[] = {'H', 'e', 'r', 'e', ' ', 'I', ' ', 'A', 'm', ' '};
int length;
len(&length, str);
printf("str's length is %dn", length);
return 0;
}
输出：
str's length is 9
注意：C/C++编译器中，数组作为参数传递，会把数组优化为指针。
字符串转数字
#include
#include
int main() {
char * str = "99";
char * str2 = "4.596";
char * str3 = "16.88x";
char * str4 = "xyz186";
int i = atoi(str);
int i2 = atoi(str2);
int i3 = atoi(str3);
int i4 = atoi(str4);
printf("i = %d, i2 = %d, i3 = %d, i4 = %dn", i, i2, i3, i4);
long l = atol(str);
long l2 = atol(str2);
long l3 = atol(str3);
long l4 = atol(str4);
printf("l = %ld, l2 = %ld, l3 = %ld, l4 = %ldn", l, l2, l3, l4);
double d = atof(str);
double d2= atof(str2);
double d3= atof(str3);
double d4 = atof(str4);
printf("d = %lf, d2 = %lf, d3 = %lf, d4 = %lfn", d, d2, d3, d4);
return 0;
}
输出：
i = 99, i2 = 4, i3 = 16, i4 = 0 l = 99, l2 = 4, l3 = 16, l4 = 0 d = 99.000000, d2 = 4.596000, d3 = 16.880000, d4 = 0.000000
比较
#include
#include
#include
#include
#include
int main() {
char * str = "One Day";
char * str2 = "One Day";
char * str3 = "one day";
int r = strcmp(str, str2); // 区分大小写
if(r){
printf("str(%s)和str2(%s)不相等n", str, str2);
}else{
printf("str(%s)和str2(%s)相等n", str, str2);
}
int r2 = strcmp(str, str3); // 区分大小写
if(r2){
printf("str(%s)和str3(%s)不相等n", str, str3);
}else{
printf("str(%s)和str3(%s)相等n", str, str3);
}
int r3 = strcasecmp(str, str3); // 不区分大小写
if(r3){
printf("str(%s)和str3(%s)忽略大小写后不相等n", str, str3);
}else{
printf("str(%s)和str3(%s)忽略大小写后相等n", str, str3);
}
return 0;
}
输出：
str(One Day)和str2(One Day)相等 str(One Day)和str3(one day)不相等 str(One Day)和str3(one day)忽略大小写后相等
查找和包含
查找到了就是包含，否则就是不包含。
#include#include int main() { char * str = "Do You Love Me?"; char * substr = "L"; char * result = strstr(str, substr); if(result) { printf("在'%s'中找到了'%s'n", str, substr); printf("result = %sn", result); printf("'%s'在'%s'中的位置是：%dn", substr, str, result - str); printf("'%s'"包含"'%s'n", str, substr); }else{ printf("在'%s'没找到了'%s'n", str, substr); printf("'%s'"不包含"'%s'n", str, substr); } return 0; }
输出：
在'Do You Love Me?'中找到了'L' result = Love Me? 'L'在'Do You Love Me?'中的位置是：7 'Do You Love Me?'"包含"'L'
拷贝和拼接
#include
#include
int main(){
char * result = malloc(100);
char * to = "--到--", *cpp = "C++", *java = "Java";
if(result){
strcpy(result, java);
printf("result = %sn", result);
strcat(result, to);
printf("result = %sn", result);
strcat(result, cpp);
printf("result = %sn", result);
free(result);
result = NULL;
}
return 0;
}
输出：
result = Java result = Java--到-- result = Java--到--C++
大小写转换
利用ctype头文件中的tolower和toupper方法编写字符串的大小写转换方法。
#include#include void lower(char *result, char *str) { char *tmp = str; while (*tmp) { *result = tolower(*tmp); result++; tmp++; } } void upper(char *result, char *str) { char *tmp = str; while (*tmp) { *result = toupper(*tmp); result++; tmp++; } } int main() { char *str = "Yesterday once More"; char *low, *up; lower(low, str); upper(up, str); printf("low = %snup = %sn", low, up); return 0; }
输出：
low = yesterday once more up = YESTERDAY onCE MORE
