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57 lines
1.8 KiB
Markdown
57 lines
1.8 KiB
Markdown
# [1329. Sort the Matrix Diagonally](https://leetcode.com/problems/sort-the-matrix-diagonally/)
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## 题目
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A **matrix diagonal** is a diagonal line of cells starting from some cell in either the topmost row or leftmost column and going in the bottom-right direction until reaching the matrix's end. For example, the **matrix diagonal** starting from `mat[2][0]`, where `mat` is a `6 x 3` matrix, includes cells `mat[2][0]`, `mat[3][1]`, and `mat[4][2]`.
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Given an `m x n` matrix `mat` of integers, sort each **matrix diagonal** in ascending order and return *the resulting matrix*.
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**Example 1:**
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```
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Input: mat = [[3,3,1,1],[2,2,1,2],[1,1,1,2]]
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Output: [[1,1,1,1],[1,2,2,2],[1,2,3,3]]
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```
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**Constraints:**
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- `m == mat.length`
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- `n == mat[i].length`
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- `1 <= m, n <= 100`
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- `1 <= mat[i][j] <= 100`
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## 题目大意
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给你一个 m * n 的整数矩阵 mat ，请你将同一条对角线上的元素（从左上到右下）按升序排序后，返回排好序的矩阵。
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## 解题思路
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- 这道题思路很简单。按照对角线，把每条对角线的元素读取出来放在数组中。这里可以利用 map 保存这些数组。再将这些数组排序。最后按照对角线还原矩阵即可。
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## 代码
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```go
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package leetcode
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func diagonalSort(mat [][]int) [][]int {
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m, n, diagonalsMap := len(mat), len(mat[0]), make(map[int][]int)
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for i := 0; i < m; i++ {
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for j := 0; j < n; j++ {
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diagonalsMap[i-j] = append(diagonalsMap[i-j], mat[i][j])
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}
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}
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for _, v := range diagonalsMap {
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sort.Ints(v)
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}
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for i := 0; i < m; i++ {
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for j := 0; j < n; j++ {
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mat[i][j] = diagonalsMap[i-j][0]
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diagonalsMap[i-j] = diagonalsMap[i-j][1:]
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}
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}
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return mat
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}
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``` |