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📜  根据给定条件将整数N减小为1的最小成本

📅  最后修改于: 2021-04-21 22:51:37             🧑  作者: Mango

给定四个整数N,X,PQ ,任务是通过以下两个操作找到使N变为1的最小成本:

  • 从N中减去1 ,成本为P。
  • N除以X (如果N可被X整除),则成本为Q。

例子:

方法:此问题可以使用贪婪方法解决。以下是观察结果:

  1. 如果x = 1,则答案为(N – 1)*P
  2. 否则,如果N小于X ,则只能将数字减1,因此答案为(N – 1)*P
  3. 否则,请执行第一个运算,直到N无法被X整除
  4. 通过比较第一操作和第二操作来最佳选择第二操作,即,如果我们可以执行第一操作以使将N减少到1的成本最小,则选择第二操作。

下面是上述方法的实现:

C++
// C++ program for the above approach
#include 
using namespace std;
  
// Function to find the minimum cost
// to reduce the integer N to 1
// by the given operations
int min_cost(int n, int x, int p, int q)
{
    // Check if x is 1
    if (x == 1) {
  
        // Print the answer
        cout << (n - 1) * p << endl;
        return 0;
    }
  
    // Prestore the answer
    int ans = (n - 1) * p;
    int pre = 0;
  
    // Iterate till n exists
    while (n > 1) {
  
        // Divide N by x
        int tmp = n / x;
  
        if (tmp < 0)
            break;
  
        pre += (n - tmp * x) * p;
  
        // Reduce n by x
        n /= x;
  
        // Add the cost
        pre += q;
  
        // Update the answer
        ans = min(ans,
                  pre + (n - 1) * p);
    }
  
    // Return the answer
    return ans;
}
  
// Driver Code
int main()
{
    // Initialize the variables
    int n = 5, x = 2, p = 2, q = 3;
  
    // Function call
    cout << min_cost(n, x, p, q);
    return 0;
}


Java
// Java program for the above approach
import java.util.*;
  
class GFG{
  
// Function to find the minimum cost
// to reduce the integer N to 1
// by the given operations
static int min_cost(int n, int x, 
                    int p, int q)
{
      
    // Check if x is 1
    if (x == 1) 
    {
  
        // Print the answer
        System.out.println((n - 1) * p); 
        return 0;
    }
  
    // Prestore the answer
    int ans = (n - 1) * p;
    int pre = 0;
  
    // Iterate till n exists
    while (n > 1)
    {
  
        // Divide N by x
        int tmp = n / x;
  
        if (tmp < 0)
            break;
  
        pre += (n - tmp * x) * p;
  
        // Reduce n by x
        n /= x;
  
        // Add the cost
        pre += q;
  
        // Update the answer
        ans = Math.min(ans,
                       pre + (n - 1) * p);
    }
  
    // Return the answer
    return ans;
}
  
// Driver code
public static void main(String[] args)
{
      
    // Initialize the variables
    int n = 5, x = 2, p = 2, q = 3;
      
    // Function call
    System.out.println(min_cost(n, x, p, q));
}
}
  
// This code is contributed by offbeat


Python3
# Python3 program for the above approach
  
# Function to find the minimum cost
# to reduce the integer N to 1
# by the given operations
def min_cost(n, x, p, q):
    
  # Check if x is 1
  if (x == 1):
  
    # Print the answer
    print((n - 1) * p)
    return 0
    
  # Prestore the answer
  ans = (n - 1) * p
  pre = 0
    
  # Iterate till n exists
  while (n > 1):
      
    # Divide N by x
    tmp = n // x
      
    if (tmp < 0):
      break
        
    pre += (n - tmp * x) * p
      
    # Reduce n by x
    n //= x
      
    # Add the cost
    pre += q
      
    # Update the answer
    ans = min(ans, pre + (n - 1) * p)
  
  # Return the answer
  return ans
  
# Driver Code
if __name__ == '__main__':
    
  # Initialize the variables
  n = 5; x = 2;
  p = 2; q = 3;
  
  # Function call
  print(min_cost(n, x, p, q))
  
# This code is contributed by mohit kumar 29


C#
// C# program for the above approach
using System;
  
class GFG{
  
// Function to find the minimum cost
// to reduce the integer N to 1
// by the given operations
static int min_cost(int n, int x, 
                    int p, int q)
{
      
    // Check if x is 1
    if (x == 1) 
    {
  
        // Print the answer
        Console.WriteLine((n - 1) * p); 
        return 0;
    }
  
    // Prestore the answer
    int ans = (n - 1) * p;
    int pre = 0;
  
    // Iterate till n exists
    while (n > 1)
    {
  
        // Divide N by x
        int tmp = n / x;
  
        if (tmp < 0)
            break;
  
        pre += (n - tmp * x) * p;
  
        // Reduce n by x
        n /= x;
  
        // Add the cost
        pre += q;
  
        // Update the answer
        ans = Math.Min(ans,
                       pre + (n - 1) * p);
    }
  
    // Return the answer
    return ans;
}
  
// Driver code
public static void Main(String[] args)
{
      
    // Initialize the variables
    int n = 5, x = 2, p = 2, q = 3;
      
    // Function call
    Console.WriteLine(min_cost(n, x, p, q));
}
}
  
// This code is contributed by princiraj1992


输出:
7

时间复杂度: O(N)
辅助空间: O(1)