[Leetcode][python]Pascal's Triangle/Pascal's Triangle II/杨辉三角/杨辉三角 II

class Solution(object):
    def generate(self, numRows):
        """
        :type numRows: int
        :rtype: List[List[int]]
        """
        if numRows == 0:
            return []
        ans = []
        for i in range(numRows):
            row = []
            for j in range(i+1):
                row.append(1)
            if i > 1:
                for x in range(i - 1):
                    row[x+1] = ans[i-1][x] + ans[i-1][x+1]
            print row
            ans.append(row)
        return ans

class Solution(object):
    def getRow(self, rowIndex):
        """
        :type rowIndex: int
        :rtype: List[int]
        """
        rowIndex += 1
        ans = []
        if rowIndex == 0:
            return []
        for i in range(rowIndex):
            this = []
            for j in range(i+1):
                this.append(1)
            if i > 1:
                for x in range(i - 1):
                    this[x+1] = ans[i-1][x] + ans[i-1][x+1]
            print this
            ans.append(this)

        return ans[rowIndex - 1]

def get_num(i, j):
    # 三种特例，左边右边最上面
    if i == j:
        return 1
    if i == 0:
        return 1
    if i > 0 and j == 0:
        return 1
    # 输入有误返回False
    if i < j:
        return False
    else:
        return get_num(i - 1, j - 1) + get_num(i - 1, j)

print(get_num(7, 2))