回溯算法77

77组合

class Solution:
    def __init__(self):
        self.path = []
        self.result = []

    def combine(self, n: int, k: int) -> List[List[int]]:
        self.backTracking(n, k, 1)
        return self.result

    def backTracking(self, n, k, start_index) -> List:
        if len(self.path) == k:
            self.result.append(self.path[:])
            return
        for i in range(start_index, n + 1):
            self.path.append(i)
            self.backTracking(n, k, i + 1)
            self.path.pop()