C++ pushing back a string by value in a vector - c++

Question

I'm doing some algorithmics problem and I'm having trouble with managing functions, vectors and strings in C++.
I have to find a concrete path in a matrix and for that, I need to have all the different paths, so I decided to use a function. This function will check where to continue to search. Here is the code of the function:
vector<string> get_all_paths(string actual, int rows, int columns, int col_actual, int row_prev) {
vector<string> solutions;
int row_actual = (rows+row_prev-1)%rows;
for (int i = 0; i < 3; i++) {
cout << col_actual << " " << row_actual << "\n";
//cout << (dp[row_prev][col_actual+1] - matrix[row_prev][col_actual+1]) << " " << dp[row_actual][col_actual] << "\n";
if( (dp[row_prev][col_actual+1] - matrix[row_prev][col_actual+1]) == dp[row_actual][col_actual] ) {
if (col_actual > 0) {
//cout << "--" << actual << " " << row_actual << "\n";
string branch = actual + to_string(row_actual+1) + " ";
solutions = get_best_path(branch, rows, columns, col_actual-1, row_actual);
//cout << ".." << actual << "\n";
} else {
//cout << actual << " " << row_actual << "\n";
cout << actual << "\n";
string branch = actual.c_str();
branch += to_string(row_actual+1);
cout << branch << "\n";
solutions.push_back( branch );
break;
}
}
row_actual = (row_actual+1)%rows;
}
for(auto i : solutions) cout << "--" << i << "\n";
return solutions;
}
And here is the call to the method:
vector<string> solutions;
for (int i = 0; i < rows; i++) {
if (dp[i][cols-1] == min_path) {
cout << "................\n";
solutions = get_best_path( (to_string(i+1)+" "), rows, cols, cols-2, i);
for(auto i : solutions) {
reverse(i.begin(), i.end());
cout << i << "\n";
}
cout << "xxxxxxxxxxxxxxx\n";
}
}
The thing is that I'm getting three paths for a given example, which is correct, but they are all the same string, which is the last path or the last change done in variable branch.
Maybe I'm mixing a lot of concepts and maybe this has been answered a lot of times, but I've searched this and got nothing.
EDIT: I'm not getting three paths from the function, just the last one, but when printing inside the function the paths i do have three inside that function all with the same value, sorry about that.
EDIT2: The idea of the problem is to find the minimum cost path in a given matrix and, if there are more than 1, the one that is the smallest lexicographically. So given a matrix:
5 4
9 1 9 9
1 9 9 9
9 9 9 9
1 1 1 1
9 9 1 9
My approach is to use dp as a matrix with the dynamic programming results and then i try to recreate all the paths in the function above.
In this case, the dp matrix is:
9 2 11 12
1 10 11 20
9 10 11 12
1 2 3 4
9 10 3 12
And so, the best paths are:
4 4 4 4
4 5 4 4
2 1 5 4
And the one correct is the last one.
Inside my function i do get the different paths and i add them to the vector of results, but then i lose them when searching for more.
Thanks for the time if you have read this :D!

Answer 1

Well I think the problem is here
solutions = get_best_path(branch, rows, columns, col_actual-1, row_actual);
because that assignment replaces any solutions you might have found so far. Instead you should append any solutions returned to any that you've found so far. In other words something like this
vector<string> tmp = get_best_path(branch, rows, columns, col_actual-1, row_actual);
solutions.insert(solutions.end(), tmp.begin(), tmp.end());
But this is just intuition, I haven't tested anything.