1.定义概述
Floyd-Warshall算法(Floyd-Warshall algorithm)是解决任意两点间的最短路径的一种算法,可以正确处理有向图或负权的最短路径问题,同时也被用于计算有向图的传递闭包。
2.实例演示
/**
* 弗洛伊德算法求最短路径
* @author sunbufu
*
*/
public class ShortestPathFloyd {
/**无穷大*/
final static int INF = Integer.MAX_VALUE;
public static void main(String[] args) {
int[] points = { 1, 2, 3, 4, 5, 6 };
int[][] weights = {
// 1 2 3 4 5 6
{0, 7, 9, INF, INF, 14 },//1
{7, 0, 10, 15, INF, INF },//2
{9, 10, 0, 11, INF, 2 },//3
{INF, 15, 11, 0, 6, INF },//4
{INF, INF, INF, 6, 0, 9 },//5
{14, INF, 2, INF, 9, 0 } //6
};
int[][] previousPoint = {
// 1 2 3 4 5 6
{1, 2, 3, 4, 5, 6 },//1
{1, 2, 3, 4, 5, 6 },//2
{1, 2, 3, 4, 5, 6 },//3
{1, 2, 3, 4, 5, 6 },//4
{1, 2, 3, 4, 5, 6 },//5
{1, 2, 3, 4, 5, 6 } //6
};
floyd(points, weights, previousPoint);
}
private static void floyd(int[] points, int[][] weights, int[][] previousPoint) {
int pointsNumber = points.length;
for(int k = 0; k < pointsNumber; k ++){
for(int i = 0; i < pointsNumber; i ++){
for(int j = 0; j < pointsNumber; j ++){
if(weights[i][k] != INF && weights[k][j] != INF && (weights[i][k] + weights[k][j]) < weights[i][j]){
weights[i][j] = weights[i][k] + weights[k][j];
previousPoint[i][j] = k;
}
}
}
}
System.out.println(weights);
}
}
3.总结
简洁的解决了最短路径问题,但是时间复杂度为O(n^3)
。