Observing that the element in the array is just iterative combination C_m_n, with m is the rowIndex and n is from 0 to rowIndex. What's more we can get the relationship between previous element and the current element to be calulated as defined in cmn function.

```
class Solution(object):
def cmn(self, m, n, last):
return last*(m+1-n)/n
def getRow(self, rowIndex):
ret=[1]
for i in range(rowIndex):
ret.append(self.cmn(rowIndex, i+1, ret[i]))
return ret
```