LeetCode 566.Reshape the Matrix

566.Reshape the Matrix

一、问题描述

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.

二、输入输出

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.

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.

三、解题思路

• 首先判断reshape之后的数组个数是不是超了原来的，如果是就直接返回原来的数组
• 将原来的数组按排连在一起，放到一个新的数组里
• 按照r和 c来取出一个新的数组即可
• 注意C++ stl API的使用，熟悉vector的插入操作

class Solution {public:    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {        int rows = nums.size();        int cols = nums[rows - 1].size();        int tot = rows * cols;        if( tot < r * c){            return nums;        }        vector<int> dict;        for (int i = 0; i < rows; ++i) {            vector<int> tmp = nums[i];            dict.insert(dict.end(), tmp.begin(), tmp.end());        }        vector<vector<int>> ret;        for (int i = 0; i < r; ++i) {            vector<int> eachLine;            for (int j = 0; j < c; ++j) {                eachLine.push_back(dict[i * c + j]);            }            ret.push_back(eachLine);        }        return ret;    }};