reverse words - code review C++ code. Dec. 25, 2017 6:00 PM

reverseWords_codereview.cpp

#include <iostream>
#include <vector>

using namespace std;

void reverse(vector<char> & arr,int start,int end);
vector<char> reverseWords( const vector<char>& arr ) // "a b cd"
{
  // your code goes here
  vector<char> copy;
  vector<int> index;
  
  for(int i = 0; i < arr.size(); i ++){
    copy.push_back(arr[i]);
  }
  
  reverse(copy,0,copy.size()-1);
  
  index.push_back(-1);  
  for(int i = 0; i < copy.size(); i ++){
    if(copy[i] == ' '){
      index.push_back(i);
    }
  }
  
  if(index.size() == 1){
    return arr;
  }
  // reverse the word 
  int j = 0;
  while(j <= index.size() - 2){
     reverse(copy,index[j]+1,index[j+1]-1);
     j++;
  }
  reverse(copy,index[j]+1,copy.size()-1);
  
  return copy;
}

void reverse(vector<char> & arr,int start,int end){
  while(end > start){
    swap(arr[start++],arr[end--]);
  }
}

int main() {  
  vector<char> v = {'a',' ','b',' ','c','d'};
  vector<char> r =  reverseWords(v);
  for(int i = 0; i < r.size(); i ++){
    cout << r[i] << endl;
  }
  return 0;
}

Ask the peer to remove extra space for word reverse, use O(1) space instead of O(n).