Here is a C implementation that is doing the word reversing inlace, and it has O(n)
complexity.
char* reverse(char *str, char wordend=0)
{
char c;
size_t len = 0;
if (wordend==0) {
len = strlen(str);
}
else {
for(size_t i=0;str[i]!=wordend && str[i]!=0;i++)
len = i+1;
}
for(size_t i=0;i