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To reverse the given string using pointer

Thursday, December 4th, 2008

This is the program to reverse the given string and display. The program internally uses the logic of reversing the word.

Logic: The approach here is to reverse the string using the pointers. Reversing the string includes the reversing the each and every words in it. After accepting a string from user, it calls a function “strev” with two string pointer arguments, the source and destination. It has an iterative loop, which traces from the EOL through the beginning. Each time it copies the current letter to the destination. Finally it displays the resultant string.

The earlier program implements the same by direct method, i.e. without pointers.

#include<stdio.h>
#include<conio.h>
void strev(char *str1, char *str2);
void main()
{
        char *str1, *str2;
        clrscr();
        printf("\n\n\t ENTER A STRING...: ");
        gets(str1);
        strev(str1,str2);
        printf("\n\t THE REVERSED STRING IS...: ");
        puts(str2);
        getch();
}

void strev(char *str1, char *str2)
{
        int i = 0, len = 0, r = 0;
        while(*(str1+len)!='\0')
                len++;
        for(i=len-1; i>=0; i--)
        {
                *(str2+r) = *(str1+i);
                r++;
        }
        *(str2+r) = '\0';
}

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Ranjith

Total : 8 Comments

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8 Responses to “To reverse the given string using pointer”

  1. kamal says:
    January 24, 2009 at 10:48 am

    i need codes for yours projects
    so please send me full details
    don’t forget me
    thank uuuuuuuuuuuuuuuuuuuuu

  2. esha says:
    May 2, 2011 at 11:18 am

    char *s1;
    gets(s1);

    this is not correct as s1 is not initialized. its giving segmentation fault.

  3. Gaurav Sharma says:
    August 1, 2011 at 11:41 am

    void main(void)
    {
    uchar *str “ABCDE”;
    uchar len;
    uchar newidex = 0;

    len=0;
    while( *str != ” ) len++;

    str = revstr(str, len, newidex);
    PRINT(str);
    }

    uint* revstr(uchar *str, uchar len, uchar &index)
    {
    uchar *b;

    if(len==0)
    {
    return b;
    }
    else
    {
    b[index++] = str[len];
    revstr( str, len-1, index );
    }
    }

  4. Gaurav Sharma says:
    August 1, 2011 at 12:00 pm

    correction in above code is:
    while( *(str+len) != ” ) len++;

  5. sathyaa says:
    February 24, 2012 at 3:45 pm

    #include
    #include
    #include
    void main()
    {
    char *str,temp;
    int i,j;
    printf(“\n Enter the string: “);
    scanf(“%s”,str);
    for(i=0,j=strlen(str)-1;i<=j;i++,j–){
    temp=*(str+i);
    *(str+i)=*(str+j);
    *(str+j)=temp;
    }
    printf("%s",str);
    getch();
    }

  6. kulbhushan says:
    March 31, 2012 at 8:12 am

    IN the above program one thing i think is missing again come back to sting. if ” THis is a string”. in the above program it will be only “siht” and the loop will not come back. if we do one more codition like.
    while (*(str1) != NULL)
    {
    while (*(str1+len) != ‘ ‘)
    len++
    for(i=len-1; i>=0; i–)
    {
    *(str2+r) = *(str1+i);
    r++;
    }
    *(str2+r) = ”;
    }

  7. kulbhushan says:
    March 31, 2012 at 8:15 am

    and *(str1)= *(str1 + r);

  8. siddharth rawat says:
    September 16, 2012 at 1:36 am

    #include
    #include
    void main()
    {
    int i=0;
    while(*(a+i)!=NULL)
    {i++;}
    printf(“\n\n”);
    for(i;i>=0;i–)
    printf(“%c”,*(a+i);
    getch();
    }

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