[Vssue]0078.子集.md

[youngyangyang04]

https://www.programmercarl.com/0078.%E5%AD%90%E9%9B%86.html

[Du1in9]

private void backtracking(int[] nums, int start) {
    paths.add(new ArrayList<>(path));
    for (int i = start; i < nums.length; i++) {
        path.add(nums[i]);
        backtracking(nums, i + 1);
        path.remove(path.size() - 1);
    }
}

// 深度1: backtracking([1,2,3], 0), path = []
i = 0：path = [1]，递归 backtracking([1,2,3], 1)，加入 paths。回溯，path = []
i = 1：path = [2]，递归 backtracking([1,2,3], 2)，加入 paths。回溯，path = []
i = 2：path = [3]，递归 backtracking([1,2,3], 3)，加入 paths。回溯，path = []
// 深度2: 例: backtracking([1,2,3], 1), path = [1]
i = 1：path = [1,2]，递归 backtracking([1,2,3], 2)，加入 paths。回溯，path = [1]
i = 2：path = [1,3]，递归 backtracking([1,2,3], 3)，加入 paths。回溯，path = [1]
// 深度3: 例: backtracking([1,2,3], 2), path = [1,2]
i = 2：path = [1,2,3]，递归 backtracking([1,2,3], 3)，加入 paths。回溯，path = [1,2]

[ZYKWLJ]

说白了就是二叉树的前序遍历呗 这个回溯法的模本