finished Pascal's Triangle II

Author: JohnnyHuo

src/Pascal's Triangle II/.DS_Store

@@ -0,0 +1,60 @@
+/*
+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?*/
+
+public class Solution {
+    public ArrayList<Integer> getRow(int rowIndex) {
+        // Start typing your Java solution below
+        // DO NOT write main() function
+        ArrayList<ArrayList<Integer>>   triangle = new ArrayList<ArrayList<Integer>>();
+        for(int i = 0; i <= rowIndex; i++){
+            ArrayList<Integer> tmp = new ArrayList<Integer>();
+            tmp.add(1);
+            if(i > 0){
+                for(int j = 0; j < triangle.get(i - 1).size() - 1; j++){
+                    tmp.add(triangle.get(i - 1).get(j) + triangle.get(i - 1).get(j + 1));
+                }
+                tmp.add(1);
+            }
+            triangle.add(tmp);
+        }
+        return triangle.get(rowIndex);
+    }
+}
+
+
+//********************O(k) Solution
+/*
+如果没有这个O(k)空间的限制，那么可以一行一行迭代生成。如果要直接生成第i行，假设生成k=3，可以这样考虑这样的一个过程：
+1 0 0 0    k = 0
+1 1 0 0    k = 1
+1 1 1 0
+1 2 1 0    k = 2
+1 2 1 1
+1 2 3 1
+1 3 3 1    k = 3
+上述过程实际上就是一个in-place的迭代过程。每当生成下一行的时候，首先数组相应位置1，然后从右向左计算每一个系数。
+http://blog.csdn.net/abcbc/article/details/8982651
+*/
+
+public ArrayList<Integer> getRow(int rowIndex) {  
+  // Start typing your Java solution below  
+  // DO NOT write main() function  
+  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;  
+}