[Swift]LeetCode296. 最佳开会地点 $ Best Meeting Point

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A group of two or more people wants to meet and minimize the total travel distance. You are given a 2D grid of values 0 or 1, where each 1 marks the home of someone in the group. The distance is calculated using Manhattan Distance, where distance(p1, p2) = |p2.x - p1.x| + |p2.y - p1.y|.

For example, given three people living at (0,0), (0,4), and (2,2):

1 - 0 - 0 - 0 - 1
|   |   |   |   |
0 - 0 - 0 - 0 - 0
|   |   |   |   |
0 - 0 - 1 - 0 - 0

The point (0,2) is an ideal meeting point, as the total travel distance of 2+2+2=6 is minimal. So return 6.

Hint:

1. Try to solve it in one dimension first. How can this solution apply to the two dimension case?

---

两个或两个以上的人组成的一个小组，他们想要满足并尽量减少总的旅行距离。您将得到一个值为0或1的二维网格，其中每个1标记组中某个人的家。使用曼哈顿距离计算距离，其中距离(p1, p2) = |p2.x - p1.x| + |p2.y - p1.y|.

例如，假设有三个人生活在(0,0), (0,4)和(2,2)之间：

1 - 0 - 0 - 0 - 1
|   |   |   |   |
0 - 0 - 0 - 0 - 0
|   |   |   |   |
0 - 0 - 1 - 0 - 0

点（0,2）是一个理想的汇合点，因为2+2+2=6的总行驶距离是最小的。所以返回6。

提示：

首先试着用一维来解决它。这个解决方案如何适用于二维情况？

---

Solution:

class Solution {
    func minTotalDistance(_ grid:inout [[Int]]) -> Int {
        var rows:[Int] = [Int]()
        var cols:[Int] = [Int]()
        for i in 0..<grid.count
        {
            for j in 0..<grid[i].count
            {
                if grid[i][j] == 1
                {
                    rows.append(i)
                    cols.append(j)
                }
            }
        }
        cols.sort()
        var res:Int = 0
        var i:Int = 0
        var j:Int = rows.count - 1
        while(i < j)
        {
            res += (rows[j] - rows[i] + cols[j] - cols[i] )
            j -= 1
            i += 1
        }
        return res                
    }
}

---

点击：Playground测试

var sol = Solution()
var grid:[[Int]] = [[1,0,0,0,1],[0,0,0,0,0],[0,0,1,0,0]]
print(sol.minTotalDistance(&grid))
//Print 6