Ford-Fulkerson algorithm with capacity scaling

//
//  main.cpp
//  Ford-Fulkerson with capacity scaling
//
//  Created by Longxiang Lyu on 8/9/16.
//  Copyright (c) 2016 Longxiang Lyu. All rights reserved.
//

#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;


bool bfs(vector<vector<int>> &rGraph, vector<int> &parent, int s, int t, int delta)
{
    int V = rGraph.size();
    vector<int> visited(V, 0);      // mark all vertices as unvisited
    queue<int> q;
    q.push(s);
    visited[s] = 1;                 // mark source vertex as visited
    
    parent.clear();
    parent.resize(V);
    parent[s] = -1;
    
    while (!q.empty())
    {
        int u = q.front();          // get the first element
        q.pop();
        
        for (int v = 0; v != V; ++v)
        {
            if (visited[v] == 0 && rGraph[u][v] >= delta)
            {