Spiral_Matrix.java

https://leetcode.com/problems/spiral-matrix/
class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
       List <Integer> res = new ArrayList();
        if(matrix.length==0){
            return res;
        }
        int rowBegin = 0;
        int rowEnd = matrix.length-1;
        int columnBegin = 0;
        int columnEnd = matrix[0].length-1;
        
        while(rowBegin<=rowEnd && columnBegin<=columnEnd){
           for(int i = columnBegin;i<=columnEnd;i++){
               res.add(matrix[rowBegin][i]);
           } 
            rowBegin++;
       
        for(int i = rowBegin;i<=rowEnd;i++){
            res.add(matrix[i][columnEnd]);
        }
        columnEnd--;
        
        if(rowBegin<=rowEnd){
            for(int i = columnEnd;i>=columnBegin;i--){
                res.add(matrix[rowEnd][i]);
            }
        }
            rowEnd--;    
       if(columnBegin<=columnEnd){
           for(int  i=rowEnd;i>=rowBegin;i--){
               res.add(matrix[i][columnBegin]);
           }
       }
            columnBegin++;
        }     
        return res;
    }
}