48 Rotate Image

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up: Could you do this in-place?

Analysis

Solution 1

public void rotate(int[][] matrix) {
        int rowLength = matrix.length;
        int colLength = matrix[0].length;
        int[][] temp = new int[rowLength][colLength];
        int newRow, newCol;

        //copy
        for(int row=0; row<rowLength; row++) {
            for(int col=0; col<colLength; col++) {
                temp[row][col] = matrix[row][col];
            }
        }

        for(int row=0; row<rowLength; row++) {
            for(int col=0; col<colLength; col++) {
                newRow = col;
                newCol = colLength - 1 - row;
                matrix[newRow][newCol] = temp[row][col];
            }
        }
    }

Follow up: Solution 2

public void rotate(int[][] matrix) {
        int rowLength = matrix.length;
        int colLength = matrix[0].length;

        int maxRow, maxCol;
        if(rowLength%2 == 0) {
            maxRow = rowLength/2;
            maxCol = colLength/2;
        }else{
            maxRow = rowLength/2;
            maxCol = colLength/2 + 1;
        }

        int tempRow, tempCol;
        int newRow=0;
        int newCol=0;
        int[] temp = new int[4];
        for(int row=0; row<maxRow; row++) {
            for(int col=0; col<maxCol; col++) {
                for(int i=0; i<4; i++) {
                    if(i==0) {
                        tempRow = row;
                        tempCol = col;
                    }
                    else{
                        tempRow = newRow;
                        tempCol = newCol;
                    }
                    newRow = tempCol;
                    newCol = colLength -1 -tempRow;
                    temp[i] = matrix[newRow][newCol];
                    if(i==0){
                        matrix[newRow][newCol] = matrix[tempRow][tempCol];
                    }else{
                        matrix[newRow][newCol] = temp[i-1];
                    }
                }
            }
        }
    }