Question

I wrote a program that reverses each word in a string. For example hello and goodbye is turned into olleh dna eybdoog. My program works, however the time efficiency is o(n^2) and I probably could of written less code. I am trying not to use any of the string.functions() ( I used string.length() once). Any tips or suggestions would be appreciated.

#include <iostream>
using namespace std;
void breakString(string& me, char * otherOne, int len, int count);
void reverseString(char* s); 
 int main () {
string me=("hello and goodbye");
char * otherOne;
int len=0;
int count=0;

for (len; len<me.length()+1; len++){
    count++;
    if (me[len]=='\0') {
        otherOne=new char[count];
        len-=count-1;
        count=0;
        for (len; me[len]; len++){
            otherOne[count]=me[len];
            count++;
        }
        reverseString(otherOne);
        breakString( me, otherOne, len, count);
    }
    if (me[len]==' ' ) {
        otherOne=new char[count];
        len-=count-1;
        count=0;
for (len; me[len] != ' '; len++){
    otherOne[count]=me[len];
    count++;
}
reverseString(otherOne);
        breakString( me, otherOne, len, count);
        count=0;
        otherOne=NULL;
        delete[]otherOne;
    }

}
delete[]otherOne;
cout << me;
return 0;
}
void reverseString(char* s)  
{

int len =0;
char swap;
for (len=0; s[len] != '\0'; len++);

for ( int i=0; i<len/2; i++)
{

    swap = *(s+i);

    *(s+i)= *(s+len-i-1);

    *(s+len-i-1) = swap;


}
}


void breakString(string &me, char * otherOne, int len, int count){
len-=count;
for (count=0; otherOne[count]; count++){
    me[len]=otherOne[count];
    len++;
}
}   

Answer 1

Isn’t far simple something like

#include <iostream>

using namespace std;

int main () {
string me=("hello and goodbye");
int i,j, index=0;
char tmp;

for (i=0; i<me.length()+1; i++) 
    if (me[i] == ' ' || me[i] == '\0') {
        for(j=i-1;j>index;j--,index++) {
            tmp = me[index];
            me[index] = me[j];
            me[j] =tmp;
        }           
        index = i+1;
    }

cout << me;
return 0;
}

?

Complexity is O(n): each word is read twice (or, better, one and a half times): once since the program finds a space or a \0, then, in the nested for, the word is reversed. index indicates the word starting char.