some_common_algorithms.cpp

//Reverse characters in a string:
void reverse(char* s)  
{  
    int i;  
    char temp;  
    size_t l = strlen(s);  
      
    for (i = 0; i < (l/2); ++i) {  
       temp = s[i];  
       s[i] = s[l - i];  
       s[l - i] = temp;  
    }  
}  
/***********************************/
void reverse(char* s)  
{  
    int i;  
    size_t l = strlen(s);  
      
    for (i = 0; i < (l/2); ++i) {  
       s[i] ^= s[l - i];  
       s[l - i] ^= s[i];  
       s[i] ^= s[l - i];  
    }  
}  
/***********************************/
std::string foo = "born2c0de";  
std::reverse(foo.begin(), foo.end());  
std::cout << foo << std::endl;  

//Count the number of occurrences of a specific character in a string
#include <algorithm>  
#include <string>  
using namespace std;  
int main() {  
    string str("Count, the number,, of commas.");  
    int count = count(str.begin(), str.end(), ',');  
}  

//Remove non-numbers from a string
//if buff's content is: "hello 2 wor145+ld--1! how 19521 a*re 1254y**ou?" then the content of buff_02 will be: "21451195211254"
while (i != strlen (buff))  
{  
    if ((buff[i] >= 48) && (buff[i] <= 57))  
    {  
        buff_02[j] = buff[i];  
        i++;  
        j++;  
    }  
    else  
    {  
        i++;  
    }  
}  

//Remove non-letters from a string
//if buff's content is: "15+41-2Hel54lo **1212 Wor2ld! Ho5w Are 6996 Yo7u?" then the content of buff_02 will be: "HelloWorldHowAreYou"
while (i != strlen (buff))  
{  
    if ((buff[i] >= 65) && (buff[i] <= 90) || (buff[i] >= 97) && (buff[i] <= 122))  
    {  
        buff_02[j] = buff[i];  
        i++;  
        j++;  
    }  
    else  
    {  
        i++;  
    }  
}  
//Remove blanks from a string
//if buff's content is: "he llo wo r ld! how ar e y ou?" then the content of buff_02 will be: "helloworld!howareyou?"
int i=0, j=0;  
int len = (int)strlen(buf);  
  
while (i != len) {  
  if (buff[i] != ' ')  
    buff[j++] = buff[i];  
  i++;  
}  
  
buff[j]=0; 

//or using char pointer you may use the following variant:
char *i=(char*)buf, *j=(char*)buf;  
  
do {  
  if (*i != ' ')  
    *(j++) = *i;  
} while (*(i++));  

//Count the number of occurrences of a specific character in a string
#include <algorithm>  
#include <string>  
using namespace std;  
int main() {  
    string str("Count, the number,, of commas.");  
    int count = count(str.begin(), str.end(), ',');  
}