InterviewStreet Find Strings Solution C++

InterviewStreet Find Strings Solution C++

Problem

https://www.interviewstreet.com/challenges/dashboard/#problem/4efa210eb70ac

Algorithm

Declare a set<string> which will contain strings lexicographically ordered.
For each input string
     generate all its substrings one by one and add them  to set
For each query
     move pointer to require index in set and return the string
     if query no is greater than size of set, print Invalid.

 

 Solution

If you know better solution please post it in comments section.
//4 out of 7 test cases passed
#include<iostream>
#include<set>
#include<string>
typedef unsigned long long int big;
using namespace std;

int main() {

int n,i;
cin >> n;

set<string> s;
set<string>::iterator it;

string s1,temp;
for(i=0;i<n;i++) {   
    cin >> s1;
    int len = s1.length();
    int j,k;
    for(j=0;j<len;j++)
        for(k=len-j;k>0;k--) {
            temp = s1.substr(j,k);
            s.insert(temp);
        }                      
}

it=s.begin();
int curr = 1;
int q;
cin >> q;
big k, len;
len = s.size();
cout << len;
for(i=0;i<q;i++) {
    cin >> k;
    if(k>len) {
       cout << "INVALID\n";
       continue;
    }
    if(curr+(len/2) < k) {
      it = s.end();
      it--;
      curr = len;
    }
    if(curr-(len/2) > k) {
       it = s.begin();
       curr = 1;
    }
    if(k>curr) {
        int j= k-curr;
        while(j) { it++; j--; }
        cout << *it << endl;
        curr = k;
    }
    else if(k<curr) {
        int j=curr-k;
        while(j) { it--; j--;}
        cout << *it << endl;
        curr = k;
    }
    else cout << *it << endl;
}

cin >> i;
}