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SpiralOrder.java
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60 lines (45 loc) · 1.69 KB
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package Algorithms;
import java.util.ArrayList;
public class SpiralOrder {
public ArrayList<Integer> spiralOrder(int[][] matrix) {
ArrayList<Integer> result = new ArrayList<Integer>();
// remember such kinds of board.
if (matrix.length == 0 || matrix[0].length == 0) {
return result;
}
spiralOrderhelp(matrix, result, matrix.length, matrix[0].length);
return result;
}
// m, n: the middle m lines and n columns.
public void spiralOrderhelp(int[][] matrix, ArrayList<Integer> result, int m, int n) {
if (m <= 0 || n <= 0) {
return;
}
// setup the begin point.
int lineB = (matrix.length - m)/2;
int colB = (matrix[0].length - n)/2;
int line = lineB;
int col = colB-1; // begin from the first element.
while (col < colB+n-1) {
result.add(matrix[line][++col]);
}
while (line < lineB+m-1) {
result.add(matrix[++line][col]);
}
// eliminate the duplicate calculating.
while (col > colB && line != lineB) {
result.add(matrix[line][--col]);
}
// eliminate the duplicate calculating.
while (line > lineB+1 && col != colB) {
result.add(matrix[--line][col]);
}
spiralOrderhelp(matrix, result, m-2, n-2);
}
public static void main(String[] args) {
int[][] input = {{2,3}};
SpiralOrder test = new SpiralOrder();
ArrayList<Integer> result = test.spiralOrder(input);
System.out.printf(result.toString());
}
}