//Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
//
//Example 1:
//
//Input:
//[
//[ 1, 2, 3 ],
//[ 4, 5, 6 ],
//[ 7, 8, 9 ]
//]
//Output: [1,2,3,6,9,8,7,4,5]
//Example 2:
//
//Input:
//[
//[1, 2, 3, 4],
//[5, 6, 7, 8],
//[9,10,11,12]
//]
//Output: [1,2,3,4,8,12,11,10,9,5,6,7]
class SpiralMatrix {
public List spiralOrder(int[][] matrix) {
List result = new ArrayList();
if(matrix == null || matrix.length == 0) {
return result;
}
int rowStart = 0;
int rowEnd = matrix.length - 1;
int colStart = 0;
int colEnd = matrix[0].length - 1;
while(rowStart <= rowEnd && colStart <= colEnd) {
for(int i = colStart; i <= colEnd; i++) {
result.add(matrix[rowStart][i]);
}
rowStart++;
for(int i = rowStart; i <= rowEnd; i++) {
result.add(matrix[i][colEnd]);
}
colEnd--;
if(rowStart <= rowEnd) {
for(int i = colEnd; i >= colStart; i--) {
result.add(matrix[rowEnd][i]);
}
}
rowEnd--;
if(colStart <= colEnd) {
for(int i = rowEnd; i >= rowStart; i--) {
result.add(matrix[i][colStart]);
}
}
colStart++;
}
return result;
}
}