766. Toeplitz Matrix

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766. Toeplitz Matrix

题目描述

A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element.

Now given an M x N matrix, return True if and only if the matrix is Toeplitz.

Example 1:

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Input: matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
Output: True
Explanation:
1234
5123
9512
In the above grid, the diagonals are "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", 
"[3, 3]", "[4]", and in each diagonal all elements are the same, so the answer is True.

Example 2:

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Input: matrix = [[1,2],[2,2]]
Output: False
Explanation:
The diagonal "[1, 2]" has different elements.

Note:

  • matrix will be a 2D array of integers.
  • matrix will have a number of rows and columns in range [1, 20].
  • matrix[i][j] will be integers in range [0, 99].

题目大意

求证此矩阵是否是常对角矩阵

解题思路

按照矩阵要求遍历即可。

代码

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class Solution {
    func isToeplitzMatrix(_ matrix: [[Int]]) -> Bool {
        guard !matrix.isEmpty else { return false }
        let width = matrix.count
        let height = matrix[0].count
        for (index, row) in matrix.enumerated() {
            var i = index + 1, j = 1
            let num = row[0]
            while i < width && j < height {
                if num != matrix[i][j] { return false }
                i += 1
                j += 1
            }
        }
        for (index, column) in matrix[0].enumerated() {
            guard index > 0 else { continue }
            var i = 1, j = index + 1
            let num = column
            while i < width && j < height {
                if num != matrix[i][j] { return false }
                i += 1
                j += 1
            }
        }
        return true
    }
}
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