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How to reverse a string using a recursive function, without
swapping or using an extra memory?
- 31 Answers
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Answer / stephen
#include <iostream>
#include <string>
using namespace std;
char * reverse (char *); //function prototype
int length(char *); //function prptotype
int main()
{
int i;
char *str = new char[6], *rev = new char[6];
cin >> str;
strcpy(rev,reverse(str));
cout <<"Original "<< str << " reverse " << rev << endl;
free(str);
free(rev);
return 0;
}
int length(char *s)
{
int i;
for (i=0; *(s+i)!='\0' ; ++i);
return i;
}
char *reverse(char *s)
{
char *t;
int i, n;
n=length(s);
t = new char[n];
for (i=0; i<n; ++i)
{
*(t+i)=*(s+n-1-i);
}
*(t+i)='\0';
return t;
}
/*based off of answer 8 i took this an intialized the
pointers so that it would run, and switched it over to the
C++ standard output commands. His algorithm was correct, he
just forgot to setup the memory*/
| Is This Answer Correct ? | 10 Yes | 14 No |
Answer / stephen
#include <iostream>
#include <string>
using namespace std;
char * reverse (char *); //function prototype
int length(char *); //function prptotype
int main()
{
int i;
char *str = new char[6], *rev = new char[6];
cin >> str;
strcpy(rev,reverse(str));
cout <<"Original "<< str << " reverse " << rev << endl;
free(str);
free(rev);
return 0;
}
int length(char *s)
{
int i;
for (i=0; *(s+i)!='\0' ; ++i);
return i;
}
char *reverse(char *s)
{
char *t;
int i, n;
n=length(s);
t = new char[n]; //opps have to add 1 here or there
wont be room for a null!
for (i=0; i<n; ++i)
{
*(t+i)=*(s+n-1-i);
}
*(t+i)='\0';
return t;
}
//can only handle words 5 letters or less.
/*based off of answer 8 i took this an intialized the
pointers so that it would run, and switched it over to the
C++ standard output commands. His algorithm was correct, he
| Is This Answer Correct ? | 8 Yes | 13 No |
Answer / smbrd
#include <iostream>
using namespace std;
void rev_str(char* str, int pos=-1, char c='\0'){
if(pos >= int(strlen(str)/2))
return;
if(c != '\0'){
str[strlen(str) - pos - 1] = str[pos];
str[pos] = c;
}
rev_str(str, ++pos, str[strlen(str) - pos - 2]);
}
int main(){
char str[] = "reverse this string";
cout << str << endl;
rev_str(str);
cout << str << endl;
//:~
return 0;
}
| Is This Answer Correct ? | 7 Yes | 15 No |
Answer / mahesh auti
#include<stdio.h>
#include <string.h>
char * reverse (char *); //function prototype
int length(char *); //function prptotype
void main()
{
int i;
char *str, *rev;
clrscr();
gets(str);
strcpy(rev,reverse(str));
printf("Original %s Reverse %s", str, rev);
free(str);
free(rev);
getch();
}
int length(char *s)
{
int i;
for (i=0; *(s+i)!='\0' ; ++i);
return i;
}
char *reverse(char *s)
{
char *t;
int i, n;
n=length(s);
for (i=0; i<n; ++i)
{
*(t+i)=*(s+n-1-i);
}
*(t+i)='\0';
printf("\nOUT: %s\n", t);
return t;
}
| Is This Answer Correct ? | 17 Yes | 27 No |
Answer / shivaraj
main()
{
char str[10];
cin>>str;
int len=strlen(str);
reverse(len);
cout<<"Reversed string is: "<<str;
}
void reverse(int len)
{
static int i=0;
str[i]=str[len-1]; //put the char in last pos to first pos
for(j=len-1;j>i;j--)
str[j]=str[j-1]; //shift to right
i++;
if(i==len)
return;
reverse(len);
}
| Is This Answer Correct ? | 5 Yes | 15 No |
Answer / rafael christ
#include <iostream>
using namespace std;
char* reverse_str(char* s)
{
char* reverse = new char[1];
//char* reverse;
int i;
if(*s != '\0')
reverse = reverse_str(s+1);
i = strlen(s) - 1;
if (i >= 0)
reverse[i] = s[0];
return reverse;
}
int main(void)
{
char* str = "tsirhc oraivur odraude leafar";
cout << "original:" << endl;
cout << str << endl << endl;
cout << "reversed:" << endl;
cout << reverse_str(str) << endl;
return 0;
}
| Is This Answer Correct ? | 14 Yes | 25 No |
Answer / asdf
void reverse_string(char *string) {
if (*str) {
reverse_string(++str);
str--;
printf("%c",*str);
}
| Is This Answer Correct ? | 2 Yes | 14 No |
Answer / moinom
#include <iostream>
#include <conio>
void reverse(char a[], int s, int sc );
void reverse(char a[], int s, int sc ){
if ((sc-s)<(s-1))
{
a[sc-s]^=a[s-1];
a[s-1]^=a[sc-s];
a[sc-s]^=a[s-1];
reverse (a, s-1, sc) ;
}
}
void main (){
char a[]="ABCDEFG";
reverse(a, 7, 7);
cout<<a;
getch(); //i just use it to freeze the screen
}
| Is This Answer Correct ? | 14 Yes | 29 No |
Answer / boomer
void Rstring( char *str,int len)
{
for(int i = 0; i < (len/2); i++)
{
str[i] ^= str[len-i-1];
str[len-i-1] ^= str[i];
str[i] ^= str[len-i-1];
}
}
int main( void )
{
char str[] = "my string";
printf("Actual string is [%s]\n", str);
Rstring(str,strlen(str));
printf("Reversed string is [%s]\n", str);
}
I dont call this swaping, coz it's not, recursive creates
new incarnations of the reverse func, EXTRA MEMORY BIG
TIME!!!
| Is This Answer Correct ? | 21 Yes | 40 No |
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