566. Reshape the Matrix

题目来源【Leetcode】

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

这道题我的做法是先将矩阵按照顺序放在一个数组里面，再根据新的行列重新分配，需要注意新矩阵的元素个数是否与旧的相同

class Solution {public:    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {        if(nums.size()*nums[0].size() != r*c) return nums;        vector<vector<int>>new_nums;        vector<int>num;        for(int i = 0 ; i < nums.size(); i++){            for(int j = 0; j < nums[0].size(); j++){                num.push_back(nums[i][j]);            }        }        int count = 0;        for(int i = 0; i < r; i++){            vector<int>temp;            for(int j = 0; j < c; j++){                temp.push_back(num[count]);                count++;            }            new_nums.push_back(temp);        }        return new_nums;    }};