Pascal's Triangle/ Pascal's Triangle II

Author: gavinfish

118 Pascal's Triangle.py

@@ -0,0 +1,32 @@
+'''
+Given numRows, generate the first numRows of Pascal's triangle.
+
+For example, given numRows = 5,
+Return
+
+[
+     [1],
+    [1,1],
+   [1,2,1],
+  [1,3,3,1],
+ [1,4,6,4,1]
+]
+'''
+
+class Solution(object):
+    def generate(self, numRows):
+        """
+        :type numRows: int
+        :rtype: List[List[int]]
+        """
+        if not numRows:
+            return []
+        result = [[1]]
+        while numRows > 1:
+            result.append([1] + [a + b for a, b in zip(result[-1][:-1], result[-1][1:])] + [1])
+            numRows -= 1
+        return result
+
+
+if __name__ == "__main__":
+    assert Solution().generate(4) == [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]]

119 Pascal's Triangle II.py

@@ -0,0 +1,25 @@
+'''
+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?
+'''
+
+class Solution(object):
+    def getRow(self, rowIndex):
+        """
+        :type rowIndex: int
+        :rtype: List[int]
+        """
+        result = [1] * (rowIndex + 1)
+        for i in range(2, rowIndex + 1):
+            for j in range(1, i):
+                result[i - j] += result[i - j - 1]
+        return result
+
+
+if __name__ == "__main__":
+    assert Solution().getRow(3) == [1, 3, 3, 1]