[Swift]LeetCode657. 机器人可否返回原点 | Robot Return to Origin

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There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it completes its moves.

The move sequence is represented by a string, and the character moves[i] represents its ith move. Valid moves are R (right), L (left), U (up), and D (down). If the robot returns to the origin after it finishes all of its moves, return true. Otherwise, return false.

Note: The way that the robot is "facing" is irrelevant. "R" will always make the robot move to the right once, "L" will always make it move left, etc. Also, assume that the magnitude of the robot's movement is the same for each move.

Example 1:

Input: "UD"
Output: true 
Explanation: The robot moves up once, and then down once. All moves have the same magnitude, so it ended up at the origin where it started. Therefore, we return true.

Example 2:

Input: "LL"
Output: false
Explanation: The robot moves left twice. It ends up two "moves" to the left of the origin. We return false because it is not at the origin at the end of its moves.

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在二维平面上，有一个机器人从原点 (0, 0) 开始。给出它的移动顺序，判断这个机器人在完成移动后是否在 (0, 0) 处结束。

移动顺序由字符串表示。字符 move[i] 表示其第 i 次移动。机器人的有效动做有 R（右），L（左），U（上）和 D（下）。若是机器人在完成全部动做后返回原点，则返回 true。不然，返回 false。

注意：机器人“面朝”的方向可有可无。 “R” 将始终使机器人向右移动一次，“L” 将始终向左移动等。此外，假设每次移动机器人的移动幅度相同。

示例 1:

输入: "UD"
输出: true
解释：机器人向上移动一次，而后向下移动一次。全部动做都具备相同的幅度，所以它最终回到它开始的原点。所以，咱们返回 true。

示例 2:

输入: "LL"
输出: false
解释：机器人向左移动两次。它最终位于原点的左侧，距原点有两次 “移动” 的距离。咱们返回 false，由于它在移动结束时没有返回原点。

---

Runtime: 32 ms

Memory Usage: 19.5 MB

 1 class Solution {
 2     func judgeCircle(_ moves: String) -> Bool {
 3         var x : Int = 0 , y : Int = 0
 4         for move in moves.unicodeScalars {
 5             switch move {
 6             case "L": x -= 1
 7             case "R": x += 1
 8             case "U": y -= 1
 9             case "D": y += 1
10             default: return false
11             }
12         }
13         return x == 0 && y == 0
14     }
15 }

---

40ms

 1 class Solution {
 2     func judgeCircle(_ moves: String) -> Bool {
 3         let arr = moves.unicodeScalars
 4         var v = 0, h = 0
 5         for char in arr {
 6             switch char {
 7             case "L":
 8                 v = v + 1
 9             case "R":
10                 v = v - 1
11             case "U":
12                 h = h + 1
13             case "D":
14                 h = h - 1
15             default:
16                 continue
17             }
18         }
19         
20         if v == 0 && h == 0 {
21             return true
22         } else {
23             return false
24         }
25     }
26 }

---

40ms

 1 class Solution {
 2     func judgeCircle(_ moves: String) -> Bool {
 3         var x = 0
 4         var y = 0
 5         var hArray: [Int] = Array<Int>(repeating: 0, count: 86)
 6         var vArray: [Int] = Array<Int>(repeating: 0, count: 86)
 7         hArray[Int("L".unicodeScalars.first!.value)] = 1
 8         hArray[Int("R".unicodeScalars.first!.value)] = -1
 9 
10         vArray[Int("U".unicodeScalars.first!.value)] = 1
11         vArray[Int("D".unicodeScalars.first!.value)] = -1
12         for i in moves.unicodeScalars {
13             let move = Int(i.value)
14             x += hArray[move]
15             y += vArray[move]
16         }
17         return x == 0 && y == 0
18     }
19 }

---

52ms

 1 class Solution {
 2     func judgeCircle(_ moves: String) -> Bool {
 3                var x = 0
 4         var y = 0
 5         let arr = Array(moves)
 6 
 7         for i in 0..<moves.count {
 8             let move = arr[i]
 9             switch move {
10             case "U":
11                 y += 1
12             case "D":
13                 y -= 1
14             case "L":
15                 x += 1
16             case "R":
17                 x -= 1
18             default: fatalError()
19             }
20         }
21         return x == 0 && y == 0
22     }
23 }

---

92ms

 1 class Solution {
 2     func judgeCircle(_ moves: String) -> Bool {
 3              var x = 0
 4         var y = 0
 5         let hDic: [Character: Int] = ["L": 1, "R": -1]
 6         let vDic: [Character: Int] = ["U": 1, "D": -1]
 7         let arr = Array(moves)
 8         let count = moves.count
 9         for i in 0..<count {
10             let move = arr[i]
11             x += hDic[move] ?? 0
12             y += vDic[move] ?? 0
13         }
14         return x == 0 && y == 0
15     }
16 }

---

124ms

 1 class Solution {
 2   func judgeCircle(_ moves: String) -> Bool {
 3     var directions: [Character:Int] = [
 4       "U" : 0,
 5       "D" : 0,
 6       "L" : 0,
 7       "R" : 0
 8     ]
 9     for move in moves {
10       directions.updateValue(directions[move]! + 1, forKey: move)
11     }
12     return directions["U"] == directions["D"] && directions["L"] == directions["R"]
13   }
14 }