[LeetCode]Rotate Image

最新推荐文章于 2024-10-08 11:15:15 发布

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本文提供了一种高效的矩阵旋转算法实现，通过遍历矩阵的独立圈层并进行元素的循环交换，实现了矩阵的90度顺时针旋转。该方法避免了使用额外的空间，降低了算法的时间复杂度。

class Solution {
//the key is to find the independent circle in the matrix
public:
	void rotate(vector<vector<int> > &matrix) {
		// Start typing your C/C++ solution below
		// DO NOT write int main() function
		int n = matrix.size();
		for (int i = 0; i < n/2; ++i)
		{
			for (int j = i; j < n-1-i; ++j)
			{
				int tmp = matrix[i][j];
				matrix[i][j] = matrix[n-1-j][i];
				matrix[n-1-j][i] = matrix[n-1-i][n-1-j];
				matrix[n-1-i][n-1-j] = matrix[j][n-1-i];
				matrix[j][n-1-i] = tmp;
			}
		}
	}
};

second time

class Solution {
//consider each loop in each sub square
public:
    void rotateUtil(vector<vector<int> >& matrix, int start, int end)
    {
        if(start >= end) return;
        for(int i = 0; i < end-start; ++i)
        {
            int tmp = matrix[start][start+i];
            matrix[start][start+i] = matrix[end-i][start];
            matrix[end-i][start] = matrix[end][end-i];
            matrix[end][end-i] = matrix[start+i][end];
            matrix[start+i][end] = tmp;
        }
        rotateUtil(matrix, start+1, end-1);
    }
    void rotate(vector<vector<int> > &matrix) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        rotateUtil(matrix, 0, matrix.size()-1);
    }
};