Reverse Words in a String II in C++

Suppose we have one input string, we have to reverse the strings word by word.

So, if the input is like ["t","h","e"," ","m","a","n"," ","i","s"," ","n","l","c","e"], then the output will be ["n","l","c","e"," ","i","s"," ","m","a","n"," ","t","h","e"]

To solve this, we will follow these steps −

• reverse the array s

• j := 0

• n := size of s

• for initialize i := 0, when i < n, update (increase i by 1), do −

  • if s[i] is same as ' ', then −

    • reverse the array s from index j to i

    • j := i + 1

• reverse the array s from index j to n

Example 

Let us see the following implementation to get better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto< v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
class Solution {
public:
   void reverseWords(vector<char>& s) {
      reverse(s.begin(), s.end());
      int j = 0;
      int n = s.size();
      for(int i = 0; i < n; i++){
         if(s[i] == ' '){
            reverse(s.begin() + j, s.begin() + i);
            j = i + 1;
         }
      }
      reverse(s.begin() + j, s.begin() + n);
   }
};
main(){
   Solution ob;
   vector<char> v = {'t','h','e',' ','m','a','n',' ','i','s',' ','n','i','c','e'};
   ob.reverseWords(v);
   print_vector(v);
}

Input

{'t','h','e',' ','m','a','n',' ','i','s',' ','n','i','c','e'}

Output

[n, i, c, e, , i, s, , m, a, n, , t, h, e, ]