题目：
解题过程：
模式A：
num = int(input("（模式A）输入数字："))
for i in range(num): for j in range(num): if j < i + 1: print(j + 1, end=" ") else: print("", end=" ") print()
模式B：
num = int(input("（模式B）输入数字："))
for i in range(num): for j in range(num): if j < (num - i): if j != (num - i - 1): print(j + 1, end=" ") else: print(j + 1, end=" ") else: print(" ", end=" ") print()
模式C：
num = int(input("（模式C）输入数字："))
for i in range(1, num + 1): for _ in range(num - i): print(" ", end=" ") for j in range(i, 0, -1): print(j, end=" ") print()
模式D：
num = int(input("（模式D）输入数字："))
for i in range(num): for j in range(num): if j >= i: print(j - i + 1, end=" ") else: print(" ", end=" ") print()
