其他

核心算法

全排列

from itertools import permutations, combinations

# 全排列
for perm in permutations(arr):
    print(list(perm))  # [1, 2, 3]

# 组合
for comb in combinations(arr, r):
    pass

差分数组

diff = [0] * (n + 1)

# 对区间 [l, r] 加 v
diff[l] += v
diff[r+1] -= v

# 还原
arr = [0] * n
curr = 0
for i in range(n):
    curr += diff[i]
    arr[i] = curr