文档讲解：491.递增子序列、46.全排列、47.全排列 II

题目链接：491.递增子序列、46.全排列、47.全排列 II

491.递增子序列

class Solution {List<List<Integer>> res = new ArrayList<>();List<Integer> path = new ArrayList<>();public List<List<Integer>> findSubsequences(int[] nums) {backTracing(nums, 0);return res;}public void backTracing(int[] nums, int index){if(path.size()>=2){res.add(new ArrayList<>(path));}HashSet<Integer> set = new HashSet<>();for(int i=index;i<nums.length; i++){if(!path.isEmpty() && path.get(path.size()-1)>nums[i] || set.contains(nums[i]))continue;set.add(nums[i]);path.add(nums[i]);backTracing(nums, i+1);path.remove(path.size()-1);}}
}

46.全排列

class Solution {List<List<Integer>> res = new ArrayList<>();List<Integer> path = new ArrayList<>();boolean[] used;public List<List<Integer>> permute(int[] nums) {if (nums.length == 0){return res;}used = new boolean[nums.length];backTracing(nums, 0);return res;}public void backTracing(int[] nums, int index){if(path.size() == nums.length){res.add(new ArrayList<>(path));return;}for(int i=0;i<nums.length; i++){if (used[i]){continue;}used[i] = true;path.add(nums[i]);backTracing(nums, index+1);path.remove(path.size()-1);used[i] = false;}}
}

47.全排列 II

class Solution {List<List<Integer>> res = new ArrayList<>();List<Integer> path = new ArrayList<>();boolean[] used;public List<List<Integer>> permuteUnique(int[] nums) {used = new boolean[nums.length];Arrays.fill(used, false);Arrays.sort(nums);backTracing(nums, 0);return res;}public void backTracing(int[] nums, int index){if(path.size() == nums.length){res.add(new ArrayList<>(path));return;}for(int i=0; i<nums.length; i++){if (i > 0 && nums[i] == nums[i - 1] && used[i - 1] == false) {continue;}if(used[i] == false){used[i] = true;path.add(nums[i]);backTracing(nums, i+1);path.remove(path.size()-1);used[i] = false;}}}
}