比较每组二维数组以确定最大距离

Question

所以我在二维数组中有一组元素，我正在尝试确定坐标之间的最大距离。

我已经创建了一个循环来遍历每个元素，但我无法弄清楚如何只比较第一组，第二组等等。这几天我一直在尝试不同的方法，这就是我到目前为止所得到的。

使用公式： farthestDistance = Math.sqrt((Math.pow((maxX - minX), 2))+ (Math.pow((maxY-minY), 2)));

int max = cities[0][0]; //int to store the max of the i column
  int min = cities[0][0]; //int to store the max of the i column


  int maxX = cities[0][0]; //int to store the max of the i column
  int maxY = cities[0][0]; //int to store the max of the i column

  int minX = cities[0][0]; //int to store the max of the j column
  int minY = cities[0][0]; //int to store the max of the j column




 for(int y=1; y<cities[0].length; y++) { //loop through columns
       for(int x=0; x<cities[y].length; x++) { //loop through lines


            if(cities[x][y] > max) { //if the number at the column i and line j is bigger than max

                max = cities[x][y];
                maxX = cities[x][0];
                maxY = cities[0][y];
            }
            if(((cities[x][0])  < min) && (cities[0][y] < min)) { //if the number at the column i and line j is bigger than max
                min = cities[x][y];

                minX = cities[x][0];
                minY = cities[0][y];

            }


        }
    }
 System.out.println("the maxX is " +maxX+ " the minX is " + maxY);
 System.out.println("the maxX is " +minX+ " the minX is " + minY);



    }


}

对于我拥有的示例数组：
int[][] 城市 = {{-48,-4},{23,-45},{-7,-40},{-28,31},{36,24},{23,-11} ,{36,-10},{-9,21}};

并且预期的输出应该是大约 91.5259。 任何帮助/指导将不胜感激！

Answer 1

如果理解得很好，您只需执行一个双循环来评估每对城市 (i,j) 之间的距离，如果它更高，则更新最大距离。这很容易做到：

public static void main (String[] args) {
    int[][] cities = {{-48,-4},{23,-45},{-7,-40},{-28,31},{36,24},{23,-11},{36,-10},{-9,21}};

    double maxDistance = 0;
    for (int i = 0; i < cities.length-1; i++) {
        for (int j = i+1; j < cities.length; j++) {
            maxDistance = Math.max(getDistance(cities[i], cities[j]), maxDistance);
        }
    }
    System.out.println("The max distance is " + maxDistance);
}

private static double getDistance(int[] city1, int[] city2) {
    int dx = city1[0] - city2[0];
    int dy = city1[1] - city2[1];
    return Math.sqrt(dx*dx + dy*dy);
}

请注意，j 从i+1 变为cities.length，因为您只需要检查unordered pairs (i,j)，因为距离(i,j) == 距离(j,i)。

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Java 8 替代方案：

double maxDistance  = Arrays.stream(cities)
        .flatMapToDouble(city1 -> Arrays.stream(cities).mapToDouble(city2 -> getDistance(city1, city2)))
        .max()
        .orElseThrow(IllegalArgumentException::new); //Or any other exception