Sub sequence occurrence in a string

Question

Given 2 strings like bangalore and blr, return whether one appears as a subsequence of the other. The above case returns true whereas bangalore and brl returns false.

Answer 1

Greedy strategy should work for this problem.

• Find the first letter of the suspected substring (blr) in the big string (*b*angalore)
• Find the second letter starting at the index of the first letter plus one (anga*l*ore)
• Find the third letter starting at the index of the second letter plus one (o*r*e)
• Continue until you can no longer find the next letter of blr in the string (no match), or you run out of letters in the subsequence (you have a match).

Here is a sample code in C++:

#include 
#include 
using namespace std;

int main() {
    string txt = "quick brown fox jumps over the lazy dog";
    string s = "brownfoxzdog";
    int pos = -1;
    bool ok = true;
    for (int i = 0 ; ok && i != s.size() ; i++) {
        ok = (pos = txt.find(s[i], pos+1)) != string::npos;
    }
    cerr << (ok ? "Found" : "Not found") << endl;
    return 0;
}