面试题：反转字符串

#include <iostream>

void ReverseStr(std::string& str,int startIndex,int endIndex)
{
int l = startIndex + (endIndex - startIndex)/2;
for(int i=startIndex;i<=l;i++)
{
std::swap(str[i],str[endIndex+startIndex-i]);
}
}
int main(int argc, const char * argv[])
{

std::string str = "this is a test";
int len = 0;

int startIndex = 0;
int endIndex = 0;
//    printf("ccc:%s",str);
len = str.length();
for(int i=0;i<len;i++)
{
//        printf("ccc:%c",str[i]);
if(str[i] == ' ' || i==len-1)
{
if(i==len-1){
endIndex = i;
}else{
endIndex = i-1;
}
printf("startIndex:%d,endIndex:%d\n",startIndex,endIndex);
ReverseStr(str,startIndex,endIndex);
startIndex = i+1;
endIndex = i+1;
}
}
ReverseStr(str,0,len-1);
printf("result:%s",str.c_str());
return 0;
}