LeetCode [Array]: Rotate Image

Source: Internet
Author: User
Tags rotate image

LeetCode [Array]: Rotate Image

You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise ).
Follow up:
Cocould you do this in-place?

Refer to the LeetCode [Array]: Spiral Matrix II iteration idea. First, complete the rotation of the outermost ring, and then rotate the inner ring in sequence. My C ++ code is as follows:

void rotate(vector
   > &matrix) {    int beginRow = 0, endRow = matrix.size() - 1, beginCol = 0, endCol = matrix[0].size() - 1;    while (beginRow <= endRow && beginCol <= endCol) {        for (int i = 0; i < endCol - beginCol; ++i) {            int tmp                               = matrix[beginRow    ][beginCol + i];            matrix[beginRow    ][beginCol + i] = matrix[  endRow - i][beginCol      ];            matrix[  endRow - i][beginCol    ] = matrix[  endRow    ][  endCol - i];            matrix[  endRow    ][  endCol - i] = matrix[beginRow + i][  endCol    ];            matrix[beginRow + i][  endCol    ] = tmp;        }        ++beginRow; --endRow;        ++beginCol; --endCol;    }}

The idea of seeing a strange solution on Discuss is: first put the matrix upside down, and then rotate along the diagonal line between the top left and the bottom right, its C ++ code implementation is very concise:

void rotate(vector
   > &matrix) {    reverse(matrix.begin(), matrix.end());    for (unsigned i = 0; i < matrix.size(); ++i)        for (unsigned j = i+1; j < matrix[i].size(); ++j)            swap (matrix[i][j], matrix[j][i]);}

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