Find all unique substrings of a string

/*

 copyright: Puneet Sohi

 */

#include <iostream>

#include <string>

#include <vector>

#include <tr1/unordered_map>

using namespace std;

using namespace tr1;

vector<string> findSubStr(string s){

//find all unique substr of s. Hashmap used

//to filter out the duplicates

vector<string> v (1);

vector<string> v1 (1);

char c;

int i=0;

string s1, t;

string subS;

unordered_map<string, int>m;

    if(s.length() <= 1){

    c = s[0];

s1.append(1, c);

v[0] = s1;

return v;

}

c = s[0];

s1.append(1,c);

v[0] = s1;

m[s1] = 1;

    subS = s.substr(1, s.length()-1);

v1 = findSubStr(subS);

for(i=0; i < v1.size(); i++){

    t = v1[i];

if(m[t] == 0){

v.push_back(t);

m[t] = 1;

}

t = s1 + t;

if(m[t] == 0){

v.push_back(t);

m[t] = 1;

}

}

return v;

}

int main () {

int i = 0;

string s1 = "aa";

vector<string> v (1);

v = findSubStr(s1);

    while(i<v.size()){

cout << v[i] << endl;

i++;

}

    return 0;

}