java求关键路径 关键路径java代码

1，拓扑排序是关键路径的一部分。
2，关键路径长度, 其实是最远路径长度。然而，它并非最短路径的对偶问题。
3，正向算每个节点的最早开始时间, 逆向算每个节点的最晚开始时间, 设计太了。
4，最晚开始时间的初始化容易弄错, 经典算法是不好对付的。

需要连接第38天的代码，在这里贴出来

package java31to40;

import java.util.Arrays;

public class D38_Net {
	public static final int MAX_DISTANCE = 10000;
	int numNodes;
	D31_IntMatrix weightMatrix;

	public static void main(String[] args) {
		D38_Net tempNet0 = new D38_Net(3);
		System.out.println(tempNet0);
		int[][] tempMatrix1 = { { 0, 9, 3, 6 }, { 5, 0, 2, 4 }, { 3, 2, 0, 1 }, { 2, 8, 7, 0 } };
		D38_Net tempNet1 = new D38_Net(tempMatrix1);
		System.out.println(tempNet1);
		tempNet1.dijkstra(1);
		int[][] tempMatrix2 = { { 0, 7, MAX_DISTANCE, 5, MAX_DISTANCE }, { 7, 0, 8, 9, 7 },
				{ MAX_DISTANCE, 8, 0, MAX_DISTANCE, 5 }, { 5, 9, MAX_DISTANCE, 0, 15 }, { MAX_DISTANCE, 7, 5, 15, 0 } };
		D38_Net tempNet2 = new D38_Net(tempMatrix2);
		tempNet2.prim();
	}

	public D38_Net(int paraNumNodes) {
		numNodes = paraNumNodes;
		weightMatrix = new D31_IntMatrix(numNodes, numNodes);
		for (int i = 0; i < numNodes; i++) {
			Arrays.fill(weightMatrix.getData()[i], MAX_DISTANCE);
		}
	}

	public D38_Net(int[][] paraMatrix) {
		weightMatrix = new D31_IntMatrix(paraMatrix);
		numNodes = weightMatrix.getRows();
	}

	public String toString() {
		String resultString = "图的权重矩阵。\r\n" + weightMatrix;
		return resultString;
	}

	public int[] dijkstra(int paraSource) {
		int[] tempDistanceArray = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			tempDistanceArray[i] = weightMatrix.getValue(paraSource, i);
		}
		int[] tempParentArray = new int[numNodes];
		Arrays.fill(tempParentArray, paraSource);
		tempParentArray[paraSource] = -1;
		boolean[] tempVisitedArray = new boolean[numNodes];
		tempVisitedArray[paraSource] = true;
		int tempMinDistance;
		int tempBestNode = -1;
		for (int i = 0; i < numNodes - 1; i++) {
			tempMinDistance = Integer.MAX_VALUE;
			for (int j = 0; j < numNodes; j++) {
				if (tempVisitedArray[j]) {
					continue;
				}
				if (tempMinDistance > tempDistanceArray[j]) {
					tempMinDistance = tempDistanceArray[j];
					tempBestNode = j;
				}
			}
			tempVisitedArray[tempBestNode] = true;
			for (int j = 0; j < numNodes; j++) {
				if (tempVisitedArray[j]) {
					continue;
				}
				if (weightMatrix.getValue(tempBestNode, j) >= MAX_DISTANCE) {
					continue;
				}
				if (tempDistanceArray[j] > tempDistanceArray[tempBestNode] + weightMatrix.getValue(tempBestNode, j)) {
					tempDistanceArray[j] = tempDistanceArray[tempBestNode] + weightMatrix.getValue(tempBestNode, j);
					tempParentArray[j] = tempBestNode;
				}
			}
			System.out.println("到每个节点的距离: " + Arrays.toString(tempDistanceArray));
			System.out.println("每个节点的父节点: " + Arrays.toString(tempParentArray));
		}
		System.out.println("最终");
		System.out.println("到每个节点的距离: " + Arrays.toString(tempDistanceArray));
		System.out.println("每个节点的父节点: " + Arrays.toString(tempParentArray));
		return tempDistanceArray;
	}

	public int prim() {
		int tempSource = 0;
		int[] tempDistanceArray = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			tempDistanceArray[i] = weightMatrix.getValue(tempSource, i);
		}
		int[] tempParentArray = new int[numNodes];
		Arrays.fill(tempParentArray, tempSource);
		tempParentArray[tempSource] = -1;
		boolean[] tempVisitedArray = new boolean[numNodes];
		tempVisitedArray[tempSource] = true;
		int tempMinDistance;
		int tempBestNode = -1;
		for (int i = 0; i < numNodes - 1; i++) {
			tempMinDistance = Integer.MAX_VALUE;
			for (int j = 0; j < numNodes; j++) {
				if (tempVisitedArray[j]) {
					continue;
				}
				if (tempMinDistance > tempDistanceArray[j]) {
					tempMinDistance = tempDistanceArray[j];
					tempBestNode = j;
				}
			}
			tempVisitedArray[tempBestNode] = true;
			for (int j = 0; j < numNodes; j++) {
				if (tempVisitedArray[j]) {
					continue;
				}
				if (weightMatrix.getValue(tempBestNode, j) >= MAX_DISTANCE) {
					continue;
				}
				if (tempDistanceArray[j] > weightMatrix.getValue(tempBestNode, j)) {
					tempDistanceArray[j] = weightMatrix.getValue(tempBestNode, j);
					tempParentArray[j] = tempBestNode;
				}
			}
			System.out.println("每个节点的选定距离: " + Arrays.toString(tempDistanceArray));
			System.out.println("每个节点的父节点: " + Arrays.toString(tempParentArray));
		}
		int resultCost = 0;
		for (int i = 0; i < numNodes; i++) {
			resultCost += tempDistanceArray[i];
		}
		System.out.println("最终");
		System.out.println("每个节点的父节点: " + Arrays.toString(tempParentArray));
		System.out.println("总成本: " + resultCost);
		return resultCost;
	}

	public boolean[] criticalPath() {
		int tempValue;
		int[] tempInDegrees = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			for (int j = 0; j < numNodes; j++) {
				if (weightMatrix.getValue(i, j) != -1) {
					tempInDegrees[j]++;
				}
			}
		}
		System.out.println("节点的入度: " + Arrays.toString(tempInDegrees));
		int[] tempEarliestTimeArray = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			if (tempInDegrees[i] > 0) {
				continue;
			}
			System.out.println("正在删除 " + i);

			for (int j = 0; j < numNodes; j++) {
				if (weightMatrix.getValue(i, j) != -1) {
					tempValue = tempEarliestTimeArray[i] + weightMatrix.getValue(i, j);
					if (tempEarliestTimeArray[j] < tempValue) {
						tempEarliestTimeArray[j] = tempValue;
					}
					tempInDegrees[j]--;
				}
			}
		}
		System.out.println("最早开始时间: " + Arrays.toString(tempEarliestTimeArray));
		int[] tempOutDegrees = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			for (int j = 0; j < numNodes; j++) {
				if (weightMatrix.getValue(i, j) != -1) {
					tempOutDegrees[i]++;
				}
			}
		}
		System.out.println("节点的出度: " + Arrays.toString(tempOutDegrees));
		int[] tempLatestTimeArray = new int[numNodes];
		for (int i = 0; i < numNodes; i++) {
			tempLatestTimeArray[i] = tempEarliestTimeArray[numNodes - 1];
		}
		for (int i = numNodes - 1; i >= 0; i--) {
			if (tempOutDegrees[i] > 0) {
				continue;
			}
			System.out.println("正在删除 " + i);

			for (int j = 0; j < numNodes; j++) {
				if (weightMatrix.getValue(j, i) != -1) {
					tempValue = tempLatestTimeArray[i] - weightMatrix.getValue(j, i);
					if (tempLatestTimeArray[j] > tempValue) {
						tempLatestTimeArray[j] = tempValue;
					}
					tempOutDegrees[j]--;
					System.out.println("减少1，" + j + " 出度.");
				}
			}
		}
		System.out.println("最晚开始时间: " + Arrays.toString(tempLatestTimeArray));

		boolean[] resultCriticalArray = new boolean[numNodes];
		for (int i = 0; i < numNodes; i++) {
			if (tempEarliestTimeArray[i] == tempLatestTimeArray[i]) {
				resultCriticalArray[i] = true;
			}
		}
		System.out.println("临界阵列: " + Arrays.toString(resultCriticalArray));
		System.out.print("关键节点: ");
		for (int i = 0; i < numNodes; i++) {
			if (resultCriticalArray[i]) {
				System.out.print(" " + i);
			}
		}
		System.out.println();
		return resultCriticalArray;
	}
}

第39天的代码

package java31to40;

public class D39_criticalPath {
	public static final int MAX_DISTANCE = 10000;

	public static void main(String[] args) {
		D38_Net tempNet0 = new D38_Net(3);
		System.out.println(tempNet0);
		int[][] tempMatrix1 = { { 0, 9, 3, 6 }, { 5, 0, 2, 4 }, { 3, 2, 0, 1 }, { 2, 8, 7, 0 } };
		D38_Net tempNet1 = new D38_Net(tempMatrix1);
		System.out.println(tempNet1);
		tempNet1.dijkstra(1);
		int[][] tempMatrix2 = { { 0, 7, MAX_DISTANCE, 5, MAX_DISTANCE }, { 7, 0, 8, 9, 7 },
				{ MAX_DISTANCE, 8, 0, MAX_DISTANCE, 5 }, { 5, 9, MAX_DISTANCE, 0, 15, },
				{ MAX_DISTANCE, 7, 5, 15, 0 } };
		D38_Net tempNet2 = new D38_Net(tempMatrix2);
		tempNet2.prim();
		int[][] tempMatrix3 = { { -1, 3, 2, -1, -1, -1 }, { -1, -1, -1, 2, 3, -1 }, { -1, -1, -1, 4, -1, 3 },
				{ -1, -1, -1, -1, -1, 2 }, { -1, -1, -1, -1, -1, 1 }, { -1, -1, -1, -1, -1, -1 } };
		D38_Net tempNet3 = new D38_Net(tempMatrix3);
		System.out.println("-------关键路径");
		tempNet3.criticalPath();
	}
}

结果输出：

图的权重矩阵。
[[10000, 10000, 10000], [10000, 10000, 10000], [10000, 10000, 10000]]
图的权重矩阵。
[[0, 9, 3, 6], [5, 0, 2, 4], [3, 2, 0, 1], [2, 8, 7, 0]]
到每个节点的距离: [5, 0, 2, 3]
每个节点的父节点: [1, -1, 1, 2]
到每个节点的距离: [5, 0, 2, 3]
每个节点的父节点: [1, -1, 1, 2]
到每个节点的距离: [5, 0, 2, 3]
每个节点的父节点: [1, -1, 1, 2]
最终
到每个节点的距离: [5, 0, 2, 3]
每个节点的父节点: [1, -1, 1, 2]
每个节点的选定距离: [0, 7, 10000, 5, 15]
每个节点的父节点: [-1, 0, 0, 0, 3]
每个节点的选定距离: [0, 7, 8, 5, 7]
每个节点的父节点: [-1, 0, 1, 0, 1]
每个节点的选定距离: [0, 7, 5, 5, 7]
每个节点的父节点: [-1, 0, 4, 0, 1]
每个节点的选定距离: [0, 7, 5, 5, 7]
每个节点的父节点: [-1, 0, 4, 0, 1]
最终
每个节点的父节点: [-1, 0, 4, 0, 1]
总成本: 24
-------关键路径
节点的入度: [0, 1, 1, 2, 1, 3]
正在删除 0
正在删除 1
正在删除 2
正在删除 3
正在删除 4
正在删除 5
最早开始时间: [0, 3, 2, 6, 6, 8]
节点的出度: [2, 2, 2, 1, 1, 0]
正在删除 5
减少1，2 出度.
减少1，3 出度.
减少1，4 出度.
正在删除 4
减少1，1 出度.
正在删除 3
减少1，1 出度.
减少1，2 出度.
正在删除 2
减少1，0 出度.
正在删除 1
减少1，0 出度.
正在删除 0
最晚开始时间: [0, 4, 2, 6, 7, 8]
临界阵列: [true, false, true, true, false, true]
关键节点:  0 2 3 5