c++之常见字符串处理

1、atol将字符串转化为长整型

#include 
#include 
#include 

int main()
{
   long val;
   char str[20];
   
//    strcpy(str, "98993489");
   strcpy(str,"3293180212");
   val = atol(str);
   printf("字符串值 = %s, 长整型值 = %ld\n", str, val);

   strcpy(str, "runoob.com");
   val = atol(str);
   printf("字符串值 = %s, 长整型值 = %ld\n", str, val);

   return(0);
}

 

2、判断两字符串是否相等strcmp(s1,s2)==0

#include 
#include 
实现两个字符串相等比较
int main(void)
{
    char str_1[] = "abc"; 
    char str_2[] = "abc";
    char str_3[] = "ABC";
    if (strcmp(str_1, str_2) == 0)
        printf("str_1 is equal to str_2. \n");
    else
        printf("str_1 is not equal to str_2. \n");
    if (strcmp(str_1, str_3) == 0)
        printf("str_1 is equal to str_3．\n");
    else
        printf("str_1 is not equal to str_3．\n");
    return 0;
}

3、判断一字符串是否是另一字符串的前缀

#include 
#include 
using namespace std;
int main()
{
  string a="abcdefghigklmn";
  string b="abc";
  string c="abe";
  //方法1 
  int r1=strncmp(a.c_str(), b.c_str(), b.size());
  int r2=strncmp(a.c_str(), c.c_str(), c.size());
  cout <

4、判断某一字符串是否包含另一字符串

// 判断是否包含某个字符串
#include 
#include 
using namespace std;
int main()
{
  string a="abcdefghigklmn";
  string b="def";
  string c="123";
  string::size_type idx;
  idx=a.find(b);//在a中查找b.
  if(idx == string::npos )//不存在。
  cout << "not found\n";
  else//存在。
  cout <<"found\n";
  idx=a.find(c);//在a中查找c。
  if(idx == string::npos )//不存在。
  cout << "not found\n";
  else//存在。
  cout <<"found\n";
  return 0;
}