pointconcat, C++ (gcc)

Language: Layout:

//g++  7.4.0
//write a function that copies the first n bytes beginning with *s2 into the bytes beginning at the location of the first occurrence of the null character ‘\0’ after *s1, where n is the number of bytes that s2 has to be incremented before it points to the null character‘\0’;
//this code is created by Rezaul Hoque on July 24,2021; contact: jewelmrh@yahoo.com
//note: codes shared by Rezaul Hoque on rextester are not for sale; they are created and shared to facilitate the algorithm learning process; many like Hoque use this platform to practice programming ;Rezaul hopes his contribution helps others to fine tune their learning;

#include <iostream>
using namespace std;

void cat(char *, char*);
//this function is like strcat() defined in string.h; it concatenates one string at the end of the other
void cat(char * s1, char* s2){
int n =4;
int n2 = 4;
char s3[n+n2];//a buffer array is created equal to total size of s1 and s2
int l= n-1;//l is initialized to the last element of s1 as zero-based indexing is being followed here
for (int k=0;k<n;k++){
s3[k]=s1[k];//first s1 is copied into s3
}
for (int k=0;k<n2;k++){
s3[l+k]=s2[k];//then s2 is copied into s3; note index of s3 is l+k; so values of s2[0],s2[1]...are copied into s3[l+0],s3[l+1]
}
for(int k=0;k<n+n2;k++)
cout<<s3[k];
}

int main(){
char s1[]="ABC";
char s2[]= "DEF";

cout<<"Before concatenation: \n";
cout<<s1<<endl;

cout<<"After concatenation: \n";
cat(s1,s2);
return 0;
}

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Compilation time: 0.53 sec, absolute running time: 0.16 sec, cpu time: 0.01 sec, memory peak: 5 Mb, absolute service time: 0,82 sec