SpiralMatrix1

SpiralMatrix - interviewbit

 public List<Integer> spiralOrder(List<ArrayList<Integer>> a){
 	
 	if( a == null || a.isEmpty()) {
 		return null;
 	}
 	// base case 3x3 then tweak 
 	int startRow = 0; 
 	int startCol = 0; 
 	
 	int endRow= a.size();
 	int endCol = a.get(0).size();
 
	// terminating condition . 
	
	// if startRow == endRow and startCol == end Col then we print 
	//element a[startRow][Endcol], this is the element in the middle of the array
	
	
	// if only one of the conditions meet then exit because we've covered the whole matrix. 
	while (startRow <=endRow  && startCol <= endCol) {
	
	//deal with matrices that have an element in the middle/ just one element left. 
	if (startRow == endRow) && (startCol == endCol) {
		result.add(a.get(startRow).get(startCol));
		break;
	}
	
	for (int i= startRow, int j = startCol;  j<=endCol-1; j++) {
		result.add(a.get(i).get(j));//1,2
	}
	
	for (int i= startRow, int j = endCol;  i<=endRow-1; i++) {
		result.add(a.get(i).get(j));//3,6
	}
	
	for (int i= endRow, int j = endCol;  j>=startCol+1; j--) {
		result.add(a.get(i).get(j));//9,8
	}
	
	for (int i= endRow, int j = startCol;  i>=startRow+1; i--) {
		result.add(a.get(i).get(j));//7,4
	}

	startRow++;
	startCol++;
	endRow --; 
	endCol --;
	}
	
}