Java version

Pascal'sTriangleII.java

/*
Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?
*/
//6/2014
public class Solution {
    public List<Integer> getRow(int rowIndex) {
        if (rowIndex<0){
            return null;
        }
        LinkedList<Integer> current=new LinkedList<Integer>();
        LinkedList<Integer> next=new LinkedList<Integer>();
        
        current.add(1);
        int start=0;
        
        while (start<rowIndex){
            current.addFirst(0);
            current.add(0);
            
            calculateNext(current, next);
            
            LinkedList<Integer> temp=next;
            next=current;
            current=temp;
            start++;
            
        }
        
        return current;
    }
    private void calculateNext(LinkedList<Integer> current, LinkedList<Integer> next){
        if (current==null){
            return;
        }
        while (current.size()>1){
            int num1=current.pop();
            int num2=current.peek();
            next.add(num1+num2);
        }
        current.clear();
    }
}


// 3/2014
public class Solution {
    /*
    [
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]
    */
    
    /*
    [1,0,0,0]
    [1,1,0,0]
    [1,2,1,0]
    [1,3,3,1]
    
    pN=pCValue+pCLeftValue;
    */
    public ArrayList<Integer> getRow(int rowIndex) {
     if (rowIndex<0){
         return null;
     }   
     ArrayList<Integer> current=new ArrayList<Integer>();
     ArrayList<Integer> next=new ArrayList<Integer>();
     
     current.add(1);
     int level=0;
     
     while (level<rowIndex){
         level++;
         next.add(1);
         for (int i=1; i<current.size(); i++){
             
             next.add(current.get(i)+current.get(i-1));
          }
          next.add(1);
          current=next;
          next=new ArrayList<Integer>();
     }
     
     return current;
     
    }
}

// 1/2014 
public class Solution {
    public ArrayList<Integer> getRow(int rowIndex) {
        if (rowIndex<0){
            return null;
        }
        ArrayList<Integer> result=new ArrayList<Integer>(rowIndex+1);
        
        for (int i=0; i<=rowIndex; i++){
            result.add(0);
        }
        result.set(0, 1);
        for (int i=1; i<=rowIndex; i++){
            result.set(i, 1);
            for (int j=i-1; j>0; j--){
                result.set(j, result.get(j)+result.get(j-1));
            }
            
        }
        
        return result;
        
        
    }
}