面试题 01.07

Given an image represented by an N x N matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees. Can you do this in place?

Example 1:

Given matrix = [ [1,2,3], [4,5,6], [7,8,9] ],

Rotate the matrix in place. It becomes: [ [7,4,1], [8,5,2], [9,6,3] ] Example 2:

Given matrix = [ [ 5, 1, 9,11], [ 2, 4, 8,10], [13, 3, 6, 7], [15,14,12,16] ],

Rotate the matrix in place. It becomes: [ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11] ]

Solutions

• the same as problem 48

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