566. Reshape the Matrix

题目：

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 = 4Output: [[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 = 4Output: [[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:

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

思路：

本题，分为以下几个步骤：

step1:判断reshape是都可行，不可行返回原数组，可行转step2

step2:建立一个vector一维数组存储nums值

step3:维护一个迭代器指针，根据要求构建数组

代码：

class Solution {public:    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {        int n_r = nums.size(),n_c = nums[0].size();        vector<vector<int>> res;        vector<int> temp,store;        cout<<n_c<<endl;        if(r*c==n_r*n_c)        {            for(int i = 0;i<n_r;i++)            {                for(int j=0;j<n_c;j++)                {                    store.push_back(nums[i][j]);                }            }            vector<int>::iterator itr = store.begin();            for(int z = 0;z<r;z++)            {                temp.clear();                for(int y=0;y<c;y++)                {                    temp.push_back(*itr);                    itr++;                }                res.push_back(temp);            }        }        else            return nums;        return res;    }};