java NP算法样例

Sure! Here's an example of the NP algorithm implemented in Java:

import java.util.ArrayList;
import java.util.Arrays;

public class NpAlgorithmExample {
    
    public static boolean npAlgorithm(int[] set, int targetSum) {
        // Sort the set in non-decreasing order
        Arrays.sort(set);
        
        // Initialize the sum variable
        int currentSum = 0;
        
        // Create an empty list to store the subset
        ArrayList<Integer> subset = new ArrayList<>();
        
        // Call the recursive helper function to find the subset
        return findSubset(set, targetSum, 0, currentSum, subset);
    }
    
    private static boolean findSubset(int[] set, int targetSum, int index, int currentSum, ArrayList<Integer> subset) {
        // Base cases
        if (currentSum == targetSum) {
            // Print the subset
            System.out.println("Subset found: " + subset);
            return true;
        }
        
        if (currentSum > targetSum || index >= set.length) {
            return false;
        }
        
        // Recursive cases
        for (int i = index; i < set.length; i++) {
            // Add the current element to the subset
            subset.add(set[i]);
            
            // Recursive call with the next index and updated current sum
            if (findSubset(set, targetSum, i + 1, currentSum + set[i], subset)) {
                return true;
            }
            
            // Remove the current element from the subset
            subset.remove(subset.size() - 1);
        }
        
        return false;
    }
    
    public static void main(String[] args) {
        int[] set = {1, 2, 3, 4, 5};
        int targetSum = 7;
        
        System.out.println("Set: " + Arrays.toString(set));
        System.out.println("Target Sum: " + targetSum);
        
        boolean subsetFound = npAlgorithm(set, targetSum);
        
        if (!subsetFound) {
            System.out.println("No subset found!");
        }
    }
}

In this example, the NP algorithm is used to find a subset of a given set of numbers whose sum is equal to a target sum. The algorithm uses a recursive approach to iterate through all possible combinations of elements in the set. The `npAlgorithm` method is the entry point which initializes the necessary variables and calls the recursive helper function `findSubset`. The `findSubset` function checks for base cases, such as finding the subset with the target sum or exceeding the target sum, and performs recursive calls to explore different combinations of elements. Finally, the `main` method demonstrates how to use the algorithm by providing a sample set and target sum.