566. reshaping the matrix

subject ： Reshaping the matrix stay MATLAB in , There's a very useful function reshape , It can put a m x n The matrix is remodeled to another different size （r x c） The new matrix of , But keep its original data . Give you a two-dimensional array mat It means m x n matrix , And two positive integers r and c , Represent the number of rows and columns of the matrix to be reconstructed respectively . The reconstructed matrix needs to replace all elements of the original matrix with the same Row traversal order fill . If the reshape The operation is feasible and reasonable , The new reshaping matrix is output ; otherwise , Output raw matrix .

Ideas ： It means that one mn The matrix of becomes another rc Matrix , Ask if it can be achieved . Be sure that the total number of elements in the matrix is the same , Then all the elements are reassigned , Go through all the elements , Then, according to the number of new columns, put them in the corresponding position .

code

class Solution {
public:
    vector<vector<int>> matrixReshape(vector<vector<int>>& mat, int r, int c) {
    int hang = mat.size();
    int lie  = mat[0].size();
    if(hang * lie != r * c) return mat;
    else{
            vector<vector<int>> ans(r,vector<int>(c));
            for(int i=0;i<hang*lie;i++){
                ans[i/c][i%c] = mat[i/lie][i%lie];
            }
            return ans;
    }
    }
};

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