単語を反転

文字列内の単語を順番に反転する関数を作成します.ハローワードみたい!ワードになる!hello

#include <iostream>
#include <string.h>
using namespace std;
void strlcpy(char *s1, const char *s2, int n)
{
    char *s;

    for(s=s1; 0<n&&*s2!='\0';--n)
        *s++=*s2++;
    *s++='\0';
    cout<<s1<<endl;
}

int main()
{
    char *buffer;
    char str[] ="hello world!";
    int len,s,m,n,l=0;
    len=strlen(str);
    s=len-1;
    buffer=(char*) malloc(len+1);
    while(s>=0){
        if(str[s]==' '){
            buffer[l++]=str[s--];
        }else {
            n=s;
            while(s>=0&&str[s]!=' ')
                s--;
            m=s+1;
            while(m<=n){
                buffer[l++]=str[m++];
            }
        }
    }
    buffer[l]='\0';
    strlcpy(str,buffer,len);
    free(buffer);
    return 0;
}

効率化版:

#include <iostream>
#include <string>
#include <cassert>
using namespace std;

void reverseRange(char* str,int begin,int end)
{
    assert(str != NULL);
    assert(begin>=0);
    assert(end<=strlen(str)-1);
    if(begin>=end)
        return;
    while(begin<=end)
    {
        char temp = str[begin];
        str[begin] = str[end];
        str[end] = temp;
        begin++;
        end--;
    }
    return;
}

void reverseString(char* str)
{
    assert(str!=NULL);
    int start=0,end=0,length=strlen(str); 
    reverseRange(str,0,length-1);
    while(end<length){
        if(str[end]!=' '){
            start=end;
            while(end<length&&str[end]!=' ')
                end++;
            end--;
            reverseRange(str,start,end);
        }
        end++;
    }
    cout<<str<<endl;
}

int main()
{  
    char* p = "hello world!";
    char* str = (char*)malloc(sizeof(char)*(strlen(p)+1));
    strcpy(str,p);
    reverseString(str);
    free(str);
    return 0;
}