4.22

弗洛伊德算法显示各点到各点最短距离和最短路径：

static int top=Integer.MAX_VALUE;

    public static void floyd(int[][] G){

        int size=G.length;

        int D[][]=new int[G.length][G.length];

        int Path[][]=new int[G.length][G.length];

//        for(int i=0;i< size;i++){

//            for(int j=0;j< size;j++){

//                Path[i][j]=-1;

//                D[i][j]=G[i][j];

//            }

//        }

        for(int i=0;i<G.length;i++) {

            for(int j=0;j<G.length;j++) {

                D[i][j]=G[i][j];

                if(D[i][j]<top&&i!=j) {

                    Path[i][j]=i;

                }

                else {

                    Path[i][j]=-1;

                }

            }

        }

        for(int k=0;k< size;k++){

            for(int i=0;i< size;i++){

                for(int j=0;j< size;j++){

                    if(D[i][k]!=top&&D[k][j]!=top&&D[i][k]+D[k][j]< D[i][j]){

                        // 更新i和j两点间的距离

                        D[i][j]=D[i][k]+D[k][j];

                        // 更新i和j两点间的路由信息

                        Path[i][j]=Path[k][j];

                    }

                }

            }

        }

        for(int i=0;i<G.length;i++) {

            for(int j=0;j<G.length;j++) {

                System.out.print(D[i][j]+" ");

                 

            }

            System.out.println();

        }  

        System.out.println();

        for(int i=0;i<G.length;i++) {

            for(int j=0;j<G.length;j++) {

                System.out.print(Path[i][j]+" ");

                 

            }

            System.out.println();

        }

    }