[Vssue]0046.全排列.md

[youngyangyang04]

https://www.programmercarl.com/0046.%E5%85%A8%E6%8E%92%E5%88%97.html

[Du1in9]

private void backtracking(int[] nums, boolean[] used) {
    if(path.size() == nums.length){
        paths.add(new ArrayList<>(path));
        return;
    }
    for(int i = 0; i < nums.length; i++){
        if(!used[i]){
            used[i] = true;
            path.add(nums[i]);
            backtracking(nums, used);
            used[i] = false;
            path.remove(path.size() - 1);
        }
    }
}

// 深度1: backtracking([1,2,3], 0), path = [], used = [f,f,f]
i = 0：path = [1]，递归 backtracking([1,2,3], 1)。回溯，path = []
i = 1：path = [2]，递归 backtracking([1,2,3], 2)。回溯，path = []
i = 2：path = [3]，递归 backtracking([1,2,3], 3)。回溯，path = []
// 深度2: 例: backtracking([1,2,3], 1), path = [1], used = [t,f,f]
i = 0：used[0] == true, 继续遍历（去重）
i = 1：path = [1,2]，递归 backtracking([1,2,3], 2)。回溯，path = [1]
i = 2：path = [1,3]，递归 backtracking([1,2,3], 3)。回溯，path = [1]
// 深度3: 例: backtracking([1,2,3], 2), path = [1,2], used = [t,t,f]
i = 0：used[0] == true, 继续遍历（去重）
i = 1：used[1] == true, 继续遍历（去重）
i = 2：path = [1,2,3]，递归 backtracking([1,2,3], 3)。回溯，path = [1,2]