[Swift]LeetCode830. 较大分组的位置 | Positions of Large Groups

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In a string S of lowercase letters, these letters form consecutive groups of the same character.

For example, a string like S = "abbxxxxzyy"has the groups "a", "bb", "xxxx", "z"and "yy".

Call a group large if it has 3 or more characters.  We would like the starting and ending positions of every large group.

The final answer should be in lexicographic order.

Example 1:

Input: "abbxxxxzzy"
Output: [[3,6]]
Explanation: "xxxx" is the single large group with starting  3 and ending positions 6.

Example 2:

Input: "abc"
Output: []
Explanation: We have "a","b" and "c" but no large group.

Example 3:

Input: "abcdddeeeeaabbbcd"
Output: [[3,5],[6,9],[12,14]]

Note:  1 <= S.length <= 1000

---

在一个由小写字母构成的字符串 S 中，包含由一些连续的相同字符所构成的分组。

例如，在字符串 S = "abbxxxxzyy" 中，就含有 "a", "bb", "xxxx", "z" 和 "yy" 这样的一些分组。

我们称所有包含大于或等于三个连续字符的分组为较大分组。找到每一个较大分组的起始和终止位置。

最终结果按照字典顺序输出。

示例 1:

输入: "abbxxxxzzy"
输出: [[3,6]]
解释: "xxxx" 是一个起始于 3 且终止于 6 的较大分组。

示例 2:

输入: "abc"
输出: []
解释: "a","b" 和 "c" 均不是符合要求的较大分组。

示例 3:

输入: "abcdddeeeeaabbbcd"
输出: [[3,5],[6,9],[12,14]]

说明:  1 <= S.length <= 1000

---

16ms

class Solution {
    func largeGroupPositions(_ S: String) -> [[Int]] {
        var left = 0
        let chars = Array(S)
        var result = [[Int]]()
        for i in 0..<chars.count {
            if chars[left] == chars[i] {
                continue
            } else {
                if i - left >= 3 {
                    result.append([left, i - 1])
                }
                left = i 
            }
        }
        if chars.count - left >= 3 {
            result.append([left, chars.count - 1])
        }
        return result
    }
}

---

20ms

class Solution {
    func largeGroupPositions(_ S: String) -> [[Int]] {
        let chars = S.utf8CString
        var char = chars[0]
        var count = 1,start = 0
        var location: [[Int]] = []
        for i in 1..<chars.count {
            if char == chars[i] {
                count += 1
            } else {
                if count >= 3 {
                    location.append([start, start+count-1])
                }
                char = chars[i]
                start = i
                count = 1
            }
        }
        return location
    }
}

---

20ms

class Solution {
func largeGroupPositions(_ S: String) -> [[Int]] {
    var result = [[Int]]()    
    var array = Array(S)
    
    if array.count <= 2 {
        return result
    }
    
    var i = 2
    while i < array.count {
        var start = -1
        if array[i] == array[i - 1] && array[i - 1] == array[i - 2] {
            start = i - 2
        }
        if start == -1 {
            i += 1
        }
        else {
            i += 1
            while i < array.count && array[i] == array[start] {
                i += 1
            }
            result.append([start, i - 1])
        }
    }    
    return result
  }
}

---

24ms

class Solution {
    func largeGroupPositions(_ S: String) -> [[Int]] {
        let A = Array(S)
        var mem: [[Int]] = []
        var begin = 0
        var element = A[0]
        for (index, item) in A.enumerated() {
            if(item == element){
                continue
            } else {
                let gap = index-begin
                if(gap>=3){
                    let temp = [begin, index-1]
                    mem.append(temp)
                }
                begin = index
                element = item
            }
        }
        
        if(begin != -1 && A.count - begin >= 3){
            mem.append([begin, A.count-1])
        }
        return mem
    }
}

---

36ms

class Solution {
    func largeGroupPositions(_ S: String) -> [[Int]] {
        var chars = Array(S)
        let count = S.count
        var res = [[Int]]()
        var i = 0

        for j in 0..<count {
            if j == count - 1 || chars[j] != chars[j + 1] {
                if j - i + 1 >= 3 {
                    res.append([i, j])
                }
                i = j + 1
            }
        }

        return res
    }
}

---

48ms

class Solution {
    func largeGroupPositions(_ S: String) -> [[Int]] {
        var currentStart = 0
        var currentEnd = 0
        var currentChar: Character = "
"
        var result = [[Int]]()
        for (index,char) in S.enumerated() {
            if char != currentChar {
                if currentEnd - currentStart >= 2 {
                result.append([currentStart,currentEnd])
            }
                currentStart = index
                currentEnd = index
                currentChar = char
            } else {
                currentEnd = index
            }
        }
        if currentEnd - currentStart >= 2 {
            result.append([currentStart,currentEnd])
        }
        return result
    }
}