[Swift]LeetCode566. 重塑矩阵 | Reshape the Matrix

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In MATLAB, there is a very useful function called 'reshape', which can reshape a matrix into a new one with different size but keep its original data.

You're given a matrix represented by a two-dimensional array, and two positive integers r and c representing the row number and column number of the wanted reshaped matrix, respectively.

The reshaped matrix need to be filled with all the elements of the original matrix in the same row-traversing order as they were.

If the 'reshape' operation with given parameters is possible and legal, output the new reshaped matrix; Otherwise, output the original matrix.

Example 1:

Input: 
nums = 
[[1,2],
 [3,4]]
r = 1, c = 4
Output: 
[[1,2,3,4]]
Explanation:
The row-traversing of nums is [1,2,3,4]. The new reshaped matrix is a 1 * 4 matrix, fill it row by row by using the previous list.

 Example 2:

Input: 
nums = 
[[1,2],
 [3,4]]
r = 2, c = 4
Output: 
[[1,2],
 [3,4]]
Explanation:
There is no way to reshape a 2 * 2 matrix to a 2 * 4 matrix. So output the original matrix.

 Note:

1. The height and width of the given matrix is in range [1, 100].
2. The given r and c are all positive.

---

在MATLAB中，有一个非常有用的函数 reshape，它可以将一个矩阵重塑为另一个大小不同的新矩阵，但保留其原始数据。

给出一个由二维数组表示的矩阵，以及两个正整数r和c，分别表示想要的重构的矩阵的行数和列数。

重构后的矩阵需要将原始矩阵的所有元素以相同的行遍历顺序填充。

如果具有给定参数的reshape操作是可行且合理的，则输出新的重塑矩阵；否则，输出原始矩阵。

示例 1:

输入: 
nums = 
[[1,2],
 [3,4]]
r = 1, c = 4
输出: 
[[1,2,3,4]]
解释:
行遍历nums的结果是 [1,2,3,4]。新的矩阵是 1 * 4 矩阵, 用之前的元素值一行一行填充新矩阵。

示例 2:

输入: 
nums = 
[[1,2],
 [3,4]]
r = 2, c = 4
输出: 
[[1,2],
 [3,4]]
解释:
没有办法将 2 * 2 矩阵转化为 2 * 4 矩阵。 所以输出原矩阵。

注意：

1. 给定矩阵的宽和高范围在 [1, 100]。
2. 给定的 r 和 c 都是正数。

---

172ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        //创建一个二维数组      
        var res:[[Int]] = [[Int]](repeating: [Int](repeating: 0, count: c), count: r)
        let len:Int = nums.count
        if len == 0 || r * c != len * nums[0].count
        {
            return nums
        }
        var count:Int = 0
        for i in 0..<len
        {
            for j in 0..<nums[0].count
            {
                res[count / c][count % c] = nums[i][j]
                count++
            }    
        }
        return res
    }
}

/*扩展Int类，实现自增++、自减--运算符*/
extension Int{
    //++前缀:先自增再执行表达示
    static prefix func ++(num:inout Int) -> Int {
        //输入输出参数num
        num += 1
        //返回加1后的数值
        return num
    }
    //后缀++:先执行表达式后再自增
    static postfix func ++(num:inout Int) -> Int {
        //输入输出参数num
        let temp = num
        //num加1
        num += 1
        //返回加1前的数值
        return temp
    }
    //--前缀:先自减再执行表达示
    static prefix func --(num:inout Int) -> Int {
        //输入输出参数num
        num -= 1
        //返回减1后的数值
        return num
    }
    //后缀--:先执行表达式后再自减
    static postfix func --(num:inout Int) -> Int {
        //输入输出参数num
        let temp = num
        //num减1
        num -= 1
         //返回减1前的数值
        return temp
    }
}

---

36ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        if c * r != nums.count * nums[0].count{
            return nums
        }
        var res = Array(repeating: Array(repeating: 0,count: c) ,count: r)
        var count = 0
        for i in 0..<nums.count{
            for j in 0..<nums[0].count{
                res[count / c][count % c] = nums[i][j]
                count += 1
            }
        }
        
        return res
    }
}

---

36ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        guard !nums.isEmpty else {
            return [[]]
        }
    
        guard nums.count * nums[0].count == r*c else {
            return nums
        }
    
        var result = [[Int]](repeating: [Int](repeating: 0, count: c), count: r)
        var index = 0
        let arr = nums.flatMap {$0}
        for row in 0..<r {
            for col in 0..<c {
                result[row][col] = arr[index]
                index += 1
            }
        }
    
        return result
    }
}

---

40ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        let row = nums.count
        let column = nums[0].count
        
        if (row == r && column == c) || row * column != r * c {
            return nums
        }
        
        var result = [[Int]]()
        var index = 0
        for _ in 0..<r {
            var newRow = [Int]()
            for _ in 0..<c {
                newRow.append(nums[index / column][index % column])
                index += 1
            }
            result.append(newRow)
        }
        return result
    }
}

---

40ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        let rows = nums.count
        let cols = nums[0].count
        if r*c != rows*cols {
            return nums
        }
        var numbers = [Int]()
        for row in nums {
            for item in row {
                numbers.append(item)
            }
        }
        var reshaped = [[Int]]()
        var rIndex = 0
        var cIndex = 0
        var row = [Int]()
        numbers.forEach{ item in 
            if cIndex == c {
                cIndex = 0
                rIndex += 1
                reshaped.append(row)
                row.removeAll()
            }
            row.append(item)
            cIndex += 1
        }
        reshaped.append(row)
        return reshaped
    }
}

---

44ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        
        guard nums.count * nums[0].count == r * c else {
            return nums
        }
        
        var res = [[Int]]()
        var tmp = [Int]()   
        var tmpCount = 0
        
        for num in nums {        
            for n in num {             
                tmp.append(n)         
                if tmp.count >= c {
                    res.append(tmp)
                    tmp.removeAll()
                }
            }
        }
        
        return res
    }
}

---

44ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        let numbers = Array(nums.joined())
        if numbers.count != r*c {
            return nums
        }

        var reshaped = Array(repeating:[Int](), count:r)
        for count in 0..<numbers.count {
            reshaped[count/c].append(numbers[count])
        }
        return reshaped
    }
}

---

48ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        let count = nums.count * nums[0].count;
        if count != r * c {
            return nums;
        }
        var result = Array<[Int]>()
        var temp = Array<Int>()
        
        for array in nums {
            for num in array {
                temp.append(num)
                if temp.count >= c {
                    result.append(temp);
                    temp.removeAll()
                }
            }
        }
        return result;
    }
}

---

48ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        var reshapedMatrix = [[Int]]()
        
        for _ in stride(from: 0, to: r, by: 1) {
            var tempRow = [Int]()
            for _ in stride(from: 0, to: c, by: 1) {
                tempRow.append(0)
            }
            reshapedMatrix.append(tempRow)
        }
        
        let matrixSize = nums.count * nums[0].count
        let reshapedMatrixSize = r * c
        if matrixSize != reshapedMatrixSize {
            return nums
        }
        for i in stride(from: 0, to: reshapedMatrixSize, by: 1) {
            reshapedMatrix[i/c][i%c] = nums[i/nums[0].count][i%nums[0].count]
        }
        return reshapedMatrix
    }
}

---

52ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
         if nums.count * nums[0].count != r * c {
            return nums
        }
        var temp = [Int](),result2 = [[Int]]()
        for itemArray in nums {
            temp += itemArray
        }
        for i in 0..<r {
            result2.append([Int](temp[i*c..<i*c+c]))
        }
        return result2
    }
}

---

76ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        guard nums.count * nums.first!.count == r * c else {
            return nums
        }
        
        var newA = [[Int]]()
        var tmpA = [Int]()
        for subA in nums {
            tmpA += subA
        }
        
        for index in stride(from: 0, to: r * c, by: c) {
            newA.append(Array(tmpA[index..<index+c]))
        }
        
        return newA
    }
}

---

84ms

class Solution {
    func matrixReshape(_ nums: [[Int]], _ r: Int, _ c: Int) -> [[Int]] {
        var new: [Int] = []
        for temp: [Int] in nums {
            for i: Int in temp {
                new.append(i)
            }
        }
        if r * c > new.count {
            return nums
        }
        var sq: [[Int]] = []
        for j in 1...r {
            var tempSq: [Int] = []
            for a in 0..<c {
                tempSq.append(new[(j-1)*c+a])
            }
            sq.append(tempSq)
        }
        return sq
    }
}