矩阵秩转换
Rank Transform of a Matrix
题目详情
问题:矩阵秩转换
考察:数组、图、动态规划
来源:Citadel
链接:https://www.jointaro.com/interviews/questions/rank-transform-of-a-matrix/
Given an m x n matrix, return a new matrix answer where answer[row][col] is the rank of matrix[row][col].
The rank is an integer that represents how large an element is compared to other elements. It is calculated using the following rules:
- The rank is an integer starting from
1. - If two elements
pandqare in the same row or column, then:- If
p < qthenrank(p) < rank(q) - If
p == qthenrank(p) == rank(q) - If
p > qthenrank(p) > rank(q)
- If
- The rank should be as small as possible.
The test cases are generated so that answer is unique under the given rules.
Example 1:
Input: matrix = [[1,2],[3,4]] Output: [[1,2],[2,3]] Explanation: The rank of matrix[0][0] is 1 because it is the smallest integer in its row and column. The rank of matrix[0][1] is 2 because matrix[0][1] > matrix[0][0] and matrix[0][0] is rank 1. The rank of matrix[1][0] is 2 because matrix[1][0] > matrix[0][0] and matrix[0][0] is rank 1. The rank of matrix[1][1] is 3 because matrix[1][1] > matrix[0][1], matrix[1][1] > matrix[1][0], and both matrix[0][1] and matrix[1][0] are rank 2.
Example 2:
Input: matrix = [[7,7],[7,7]] Output: [[1,1],[1,1]]
Example 3:
Input: matrix = [[20,-21,14],[-19,4,19],[22,-47,24],[-19,4,19]] Output: [[4,2,3],[1,3,4],[5,1,6],[1,3,4]]
Constraints:
m == matrix.lengthn == matrix[i].length1 <= m, n <= 500-109 <= matrix[row][col] <= 109
解析
思路:按数值从小到大处理。相同数值中,如果两个位置在同一行或同一列,需要用并查集合并成一组;每组 rank 为相关行列当前最大 rank 加 1,再统一更新行列 rank。
复杂度:排序 O(mn log(mn)),并查集近似线性,空间 O(mn)。