最大化与图中所有其他节点断开连接的节点数

给定两个整数N和E ，它们表示无向图的节点数和边数，任务是最大化图中未连接到任何其他节点的节点数，而不使用任何自环。
例子：

Input: N = 5, E = 1 
Output: 3 
Explanation: 
Since there is only 1 edge in the graph which can be used to connect two nodes. 
Therefore, three node remains disconnected.

Input: N = 5, E = 2 
Output: 2

方法：该方法基于这样一种思想，即为了最大化断开连接的节点的数量，新节点将不会添加到图中，直到每两个不同的节点连接起来。下面是解决这个问题的步骤：

1. 初始化两个变量curr和rem分别存储连接的节点和未分配的边。
2. 如果rem变为 0，则所需答案将为N – curr 。
3. 否则，将curr的值增加 1。
4. 因此，当前步骤中保持每两个不同节点连接所需的最大边是min(rem, curr) 。从rem 中减去它并增加curr 。
5. 重复这个过程，直到rem减少到零。
6. 最后，打印N – curr 。

下面是上述方法的实现：

C++

// C++ implementation of
// the above approach
 
#include 
using namespace std;
 
// Function which returns
// the maximum number of
// isolated nodes
int maxDisconnected(int N, int E)
{
    // Used nodes
    int curr = 1;
 
    // Remaining edges
    int rem = E;
 
    // Count nodes used
    while (rem > 0) {
        rem = rem
              - min(
                    curr, rem);
        curr++;
    }
 
    // If given edges are non-zero
    if (curr > 1) {
        return N - curr;
    }
    else {
        return N;
    }
}
 
// Driver Code
int main()
{
    // Given N and E
    int N = 5, E = 1;
 
    // Function Call
    cout << maxDisconnected(N, E);
 
    return 0;
}

Java

// Java implementation of
// the above approach
import java.util.*;
 
class GFG{
 
// Function which returns
// the maximum number of
// isolated nodes
static int maxDisconnected(int N, int E)
{
     
    // Used nodes
    int curr = 1;
 
    // Remaining edges
    int rem = E;
 
    // Count nodes used
    while (rem > 0)
    {
        rem = rem - Math.min(
                    curr, rem);
        curr++;
    }
 
    // If given edges are non-zero
    if (curr > 1)
    {
        return N - curr;
    }
    else
    {
        return N;
    }
}
 
// Driver Code
public static void main(String[] args)
{
     
    // Given N and E
    int N = 5, E = 1;
 
    // Function call
    System.out.print(maxDisconnected(N, E));
}
}
 
// This code is contributed by 29AjayKumar

Python3

# Python3 implementation of
# the above approach
 
# Function which returns
# the maximum number of
# isolated nodes
def maxDisconnected(N, E):
 
    # Used nodes
    curr = 1
 
    # Remaining edges
    rem = E
 
    # Count nodes used
    while (rem > 0):
        rem = rem - min(curr, rem)
        curr += 1
 
    # If given edges are non-zero
    if (curr > 1):
        return N - curr
    else:
        return N
 
# Driver Code
if __name__ == '__main__':
 
    # Given N and E
    N = 5
    E = 1
 
    # Function call
    print(maxDisconnected(N, E))
 
# This code is contributed by mohit kumar 29

C#

// C# implementation of
// the above approach
using System;
class GFG{
 
// Function which returns
// the maximum number of
// isolated nodes
static int maxDisconnected(int N,
                           int E)
{   
  // Used nodes
  int curr = 1;
 
  // Remaining edges
  int rem = E;
 
  // Count nodes used
  while (rem > 0)
  {
    rem = rem - Math.Min(curr, rem);
    curr++;
  }
 
  // If given edges are non-zero
  if (curr > 1)
  {
    return N - curr;
  }
  else
  {
    return N;
  }
}
 
// Driver Code
public static void Main(String[] args)
{
  // Given N and E
  int N = 5, E = 1;
 
  // Function call
  Console.Write(maxDisconnected(N, E));
}
}
  
// This code is contributed by 29AjayKumar

输出：

3

时间复杂度： O(E)
辅助空间： O(1)

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