printElementsInSpiralOrder

static String printElementsInSpiralOrder(int[][] matrix) {          //time complexity: O(n)
		String result = null;
		List ans = new ArrayList<>();
	        if(matrix.length != 0){
	        int r1 = 0, r2 = matrix.length-1;
	        int c1 = 0, c2 = matrix[0].length-1;
	        while(r1<=r2 && c1<=c2){
	        	for(int c=c1;c<=c2;c++)
	        		ans.add(matrix[r1][c]);
	        	for(int r = r1+1;r<=r2;r++)
	        		ans.add(matrix[r][c2]);
	        		
	        		if(r1<r2 && c1<c2){
	        			for(int c = c2-1;c> c1;c--)
	        				ans.add(matrix[r2][c]);
	        			for(int r=r2;r> r1;r--)
	        				ans.add(matrix[r][c1]);
	        		}
	        	r1++;
	        	r2--;
	        	c1++;
	        	c2--;
	        	
	        		}
            }
	        result = ans.toString().replace(",", "");
	        return result;
	        }