[leetcode]566. Reshape the Matrix

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最新推荐文章于 2021-08-26 10:55:44 发布

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本文介绍了一个基于MATLAB中'reshape'功能的算法实现，该算法能够改变矩阵的形状，同时保持原有数据不变。通过两个例子详细说明了如何进行矩阵重塑，并提供了完整的Java代码实现。

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Question:

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-traversingorder 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:

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

分析：1. 只有原数组元素个数与新的元素个数下等才需要转换，否则直接返回原数组。

将矩阵横向展开为一维数组，元素个数为n=origin_r * origin_c
在元素在一维数组中对应的位置i：原矩阵位置[i/origin_c,i%origin_c]，新矩阵位置[i/c,i%c]

Solution:

/**
 * @author binkang
 * @date May 1, 2017
 */
public class Solution {
    public int[][] matrixReshape(int[][] nums, int r, int c) {
		int original_r = nums.length;
		int original_c = nums[0].length;
		if (original_r * original_c == r * c) {
			int[][] result = new int[r][c];
			for (int i = 0; i < r * c; i++) {
				result[i / c][i % c] = nums[i / original_c][i % original_c];
			}
			return result;
		} else {
			return nums;
		}
	}
}