Leetcode notes 566. Reshaping the matrix

Title Description

Topic linking
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 .

Example 1：

Input ：mat = [[1,2],[3,4]], r = 1, c = 4
Output ：[[1,2,3,4]]
Example 2：

Input ：mat = [[1,2],[3,4]], r = 2, c = 4
Output ：[[1,2],[3,4]]

Tips ：

m = mat.length
n = mat[i].length
1 <= m, n <= 100
-1000 <= mat[i][j] <= 1000
1 <= r, c <= 300

Ideas

It's pure simulation

Code

class Solution {
    
public:
    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {
    
        int m = nums.size();
        int n = nums[0].size();
        if (m * n != r * c) {
    
            return nums;
        }

        vector<vector<int>> ans(r, vector<int>(c));
        for (int x = 0; x < m * n; ++x) {
    
            ans[x / c][x % c] = nums[x / n][x % n];
        }
        return ans;
    }
};

Be careful

To learn vector Initialization method of , This is very important , Can save time .