图中的依赖总和

给定一个有 n 个节点的有向连通图。如果从 u 到 v 有一条边，那么 u 依赖于 v。我们的任务是找出每个节点的依赖关系之和。

例子：
对于图中的图形，
A 取决于 C 和 D 即 2
B 取决于 C 即 1
D 取决于 C 即 1
而 C 不依赖于任何东西。
因此答案 -> 0 + 1 + 1 + 2 = 4
提问：Flipkart 采访

想法是检查邻接列表并找出每个顶点有多少条边并返回边的总数。

C++

// C++ program to find the sum of dependencies
#include 
using namespace std;
  
// To add an edge
void addEdge(vector  adj[], int u,int v)
{
    adj[u].push_back(v);
}
  
// find the sum of all dependencies
int findSum(vector adj[], int V)
{
    int sum = 0;
  
    // just find the size at each vector's index
    for (int u = 0; u < V; u++)
        sum += adj[u].size();
  
    return sum;
}
  
// Driver code
int main()
{
    int V = 4;
    vectoradj[V];
    addEdge(adj, 0, 2);
    addEdge(adj, 0, 3);
    addEdge(adj, 1, 3);
    addEdge(adj, 2, 3);
  
    cout << "Sum of dependencies is "
         << findSum(adj, V);
    return 0;
}

Java

// Java program to find the sum of dependencies
  
import java.util.Vector;
  
class Test
{
    // To add an edge
    static void addEdge(Vector  adj[], int u,int v)
    {
        adj[u].addElement((v));
    }
      
    // find the sum of all dependencies
    static int findSum(Vector adj[], int V)
    {
        int sum = 0;
       
        // just find the size at each vector's index
        for (int u = 0; u < V; u++)
            sum += adj[u].size();
       
        return sum;
    }
      
    // Driver method
    public static void main(String[] args) 
    {
        int V = 4;
          @SuppressWarnings("unchecked")
        Vector adj[] = new Vector[V];
          
        for (int i = 0; i < adj.length; i++) {
            adj[i] = new Vector<>();
        }
          
        addEdge(adj, 0, 2);
        addEdge(adj, 0, 3);
        addEdge(adj, 1, 3);
        addEdge(adj, 2, 3);
       
        System.out.println("Sum of dependencies is " +
                            findSum(adj, V));
    }
}
// This code is contributed by Gaurav Miglani

Python3

# Python3 program to find the sum 
# of dependencies
  
# To add an edge
def addEdge(adj, u, v):
  
    adj[u].append(v)
  
# Find the sum of all dependencies
def findSum(adj, V):
      
    sum = 0
      
    # Just find the size at each 
    # vector's index
    for u in range(V):
        sum += len(adj[u])
          
    return sum
  
# Driver code
if __name__=='__main__':
  
    V = 4
    adj = [[] for i in range(V)]
      
    addEdge(adj, 0, 2)
    addEdge(adj, 0, 3)
    addEdge(adj, 1, 3)
    addEdge(adj, 2, 3)
      
    print("Sum of dependencies is",
          findSum(adj, V))
      
# This code is contributed by rutvik_56

C#

// C# program to find the sum of dependencies
using System;
using System.Collections;
  
class GFG{
      
// To add an edge
static void addEdge(ArrayList []adj, int u,
                                     int v)
{
    adj[u].Add(v);
}
  
// Find the sum of all dependencies
static int findSum(ArrayList []adj, int V)
{
    int sum = 0;
      
    // Just find the size at each 
    // vector's index
    for(int u = 0; u < V; u++)
        sum += adj[u].Count;
   
    return sum;
}
  
// Driver code
public static void Main(string[] args) 
{
    int V = 4;
        
    ArrayList []adj = new ArrayList[V];
      
    for(int i = 0; i < V; i++)
    {
        adj[i] = new ArrayList();
    }
      
    addEdge(adj, 0, 2);
    addEdge(adj, 0, 3);
    addEdge(adj, 1, 3);
    addEdge(adj, 2, 3);
   
    Console.Write("Sum of dependencies is " +
                  findSum(adj, V));
}
}
  
// This code is contributed by pratham76

输出：

Sum of dependencies is 4

时间复杂度：O(V)，其中 V 是图中的顶点数。