[Swift]LeetCode554. 砖墙 | Brick Wall

时间 2019-11-11

标签 swift leetcode554 leetcode 砖墙 brick wall 栏目 Swift 繁體版

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There is a brick wall in front of you. The wall is rectangular and has several rows of bricks. The bricks have the same height but different width. You want to draw a vertical line from the top to the bottom and cross the leastbricks.git

The brick wall is represented by a list of rows. Each row is a list of integers representing the width of each brick in this row from left to right.github

If your line go through the edge of a brick, then the brick is not considered as crossed. You need to find out how to draw the line to cross the least bricks and return the number of crossed bricks.微信

You cannot draw a line just along one of the two vertical edges of the wall, in which case the line will obviously cross no bricks. ide

Example:this

Input: [[1,2,2,1],
        [3,1,2],
        [1,3,2],
        [2,4],
        [3,1,2],
        [1,3,1,1]]

Output: 2

Explanation:

Note:spa

The width sum of bricks in different rows are the same and won't exceed INT_MAX.
The number of bricks in each row is in range [1,10,000]. The height of wall is in range [1,10,000]. Total number of bricks of the wall won't exceed 20,000.

你的面前有一堵方形的、由多行砖块组成的砖墙。这些砖块高度相同可是宽度不一样。你如今要画一条自顶向下的、穿过最少砖块的垂线。code

砖墙由行的列表表示。每一行都是一个表明从左至右每块砖的宽度的整数列表。htm

若是你画的线只是从砖块的边缘通过，就不算穿过这块砖。你须要找出怎样画才能使这条线穿过的砖块数量最少，而且返回穿过的砖块数量。blog

你不能沿着墙的两个垂直边缘之一画线，这样显然是没有穿过一块砖的。

示例：

输入: [[1,2,2,1],
      [3,1,2],
      [1,3,2],
      [2,4],
      [3,1,2],
      [1,3,1,1]]

输出: 2

解释:

提示：

每一行砖块的宽度之和应该相等，而且不能超过 INT_MAX。
每一行砖块的数量在 [1,10,000] 范围内，墙的高度在 [1,10,000] 范围内，总的砖块数量不超过 20,000。

264ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         guard !wall.isEmpty else {
 4             return 0
 5         }
 6         
 7         var sumToCount: [Int:Int] = [:]
 8         var maxCount = 0
 9         
10         for row in 0..<wall.count {
11             
12             var sum = 0
13             
14             for column in 0..<wall[row].count-1 {
15                 sum += wall[row][column]
16                 
17                 let count = sumToCount[sum, default: 0] + 1
18                 sumToCount[sum] = count
19                 
20                 maxCount = max(maxCount, count)
21             }
22         }
23         
24         return wall.count - maxCount
25     }
26 }

Runtime: 268 ms

Memory Usage: 19.1 MB

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         var mx:Int = 0
 4         var m:[Int:Int] = [Int:Int]()
 5         for a in wall
 6         {
 7             var sum:Int = 0
 8             for i in 0..<a.count - 1
 9             {
10                 sum += a[i]
11                 if m[sum] == nil
12                 {
13                     m[sum] = 1
14                 }
15                 else
16                 {
17                     m[sum]! += 1
18                 }                
19                 mx = max(mx, m[sum]!)
20             }
21         }
22         return wall.count - mx
23     }
24 }

268ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         if wall.isEmpty || wall[0].isEmpty { return 0 }
 4         
 5         var results = [Int: Int]()
 6         for i in 0..<wall.count {
 7             var idx = 0
 8             for j in 0..<wall[i].count - 1 {
 9                 idx += wall[i][j]
10                 results[idx, default:0] += 1
11             }
12         }
13         
14         return wall.count - (results.values.max() ?? 0)
15     }
16 }

352ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         var map = [Int:Int]()
 4         var minCount = wall.count
 5         wall.forEach { (ele) in
 6             var sum = 0
 7            for i in 0..<ele.count-1 {
 8                 sum += ele[i]
 9                 map[sum] = (map[sum] ?? 0) + 1
10             }
11         }
12         map.forEach { (_, value) in
13             minCount = min(minCount, wall.count - value)
14         }
15         return minCount
16     }
17 }

388ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         var map: [Int: Int] = [:]
 4         for row in wall {
 5             var sum = 0
 6             for i in 0 ..< (row.count - 1) {
 7                 sum += row[i]
 8                 map[sum] = (map[sum] ?? 0) + 1
 9             }
10         }
11         var res = wall.count
12         for key in map.keys {
13             res = min(res, wall.count - map[key]!)
14         }
15         return res
16     }
17 }

512ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3         var map: [Int:Int] = [:]
 4         for row in wall {
 5             var tmp = 0
 6             for i in 0..<(row.count - 1) {
 7                 tmp += row[i]
 8                 map[tmp] = (map[tmp] ?? 0) + 1
 9             }
10         }
11         var count = wall.count
12         for (key,val) in map {
13             count = min(wall.count - val, count)
14         }
15         return count 
16     }
17 }

640ms

 1 class Solution {
 2     func leastBricks(_ wall: [[Int]]) -> Int {
 3 guard wall.count > 0 else { return 0 }
 4     var offsetsWithHoles = Array(repeating: 0, count: 65536)
 5     for row in wall {
 6         var offset = 0
 7         for brick in row.dropLast() {
 8             offset += brick
 9             offsetsWithHoles[offset] += 1
10         }
11     }
12     return wall.count - offsetsWithHoles.max()!
13     }
14 }