C++ code to find two substrings with one minimal substring

Suppose we have a lowercase string S with n characters. We have to find two non-empty substrings P and Q, such that −

• Both P and Q are subsequences of S

• For each index i, S[i] belong to exactly one of P and Q.

• P is lexicographically minimum as possible.

So, if the input is like S = "thelightsaber", then the output will be 10, because we need 2 red notebooks, 3 green notebooks, and 5 blue notebooks.

Steps

To solve this, we will follow these steps −

c := S
sort the array c
a := position of (c[0]) in S
delete c from S
print c[0] and S

Example

Let us see the following implementation to get better understanding −

#include <bits/stdc++.h>
using namespace std;
void solve(string S){
   string c = S;
   sort(c.begin(), c.end());
   int a = S.find(c[0]);
   S.erase(S.begin() + a);
   cout << c[0] << ", " << S << endl;
}
int main(){
   string S = "thelightsaber";
   solve(S);
}

Input

"thelightsaber"

Output

a, thelightsber