566. Reshape the Matrix

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.

解题思路：将数组改为要求的数组格式，如果更改后的数组和原数组大小不匹配，返回原数组，否则返回更改后的数组。

循环遍历原数组，将原数组存储到新数组中。

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遇到的问题：1、vector数组初始化的时候，如果新数组大小不定义好，会报错vector<vector<int>>matrix(r, vector<int>(c));

2、当行数为零的时候，列数为零，要进行判断

class Solution {
public:
    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {
        vector<vector<int>>matrix(r, vector<int>(c));
        int depth=nums.size();
        int width=depth?nums[0].size():0;
        if((r*c)!=(width*depth))return nums;
        int k=0,l=0;
        for(int i=0;i<depth;i++)
            for(int j=0;j<width;j++){
                 matrix[l][k]=nums[i][j];
                if(k<c-1){
                    k++;
                }
                else{
                    l++;
                    k=0;
                }
            }
        return matrix;
    }
};

566. Reshape the Matrix

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