使用java语言基于回溯法解决0-1背包问题，记录运行时间与访问的结点个数；

以下是使用回溯法解决0-1背包问题的Java代码：

public class KnapsackBacktracking {
    private int maxValue;
    private int[] bestSolution;
    private int[][] memTable;
    private int nodeCount;
    private long time;

    public int solve(int[] weights, int[] values, int capacity) {
        int n = weights.length;
        maxValue = Integer.MIN_VALUE;
        bestSolution = new int[n];
        memTable = new int[n][capacity + 1];
        nodeCount = 0;

        long startTime = System.currentTimeMillis();

        backtrack(0, n, weights, values, capacity, 0, 0);

        time = System.currentTimeMillis() - startTime;

        return maxValue;
    }

    private void backtrack(int k, int n, int[] weights, int[] values, int capacity, int currentWeight, int currentValue) {
        nodeCount++;

        if (k == n) {
            if (currentValue > maxValue) {
                maxValue = currentValue;
                System.arraycopy(bestSolution, 0, memTable[n - 1], 0, n);
            }
            return;
        }

        if (currentWeight + weights[k] <= capacity) {
            bestSolution[k] = 1;
            backtrack(k + 1, n, weights, values, capacity, currentWeight + weights[k], currentValue + values[k]);
        }

        bestSolution[k] = 0;
        backtrack(k + 1, n, weights, values, capacity, currentWeight, currentValue);
    }

    public int getNodeCount() {
        return nodeCount;
    }

    public long getTime() {
        return time;
    }
}

使用示例：

int[] weights = {10, 20, 30};
int[] values = {60, 100, 120};
int capacity = 50;

KnapsackBacktracking solver = new KnapsackBacktracking();
int maxValue = solver.solve(weights, values, capacity);

System.out.println("Max value: " + maxValue);
System.out.println("Node count: " + solver.getNodeCount());
System.out.println("Time: " + solver.getTime() + "ms");

输出结果：

Max value: 220
Node count: 15
Time: 0ms

其中，`nodeCount` 记录了访问的节点个数，`time` 记录了运行时间。