代码随想录二刷day29

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前言

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一、力扣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) {
        // Arrays.sort(nums);
        fun(nums, 0);
        return res;
    }
    public void fun(int[] nums, int start){
        if(path.size() >= 2){
            res.add(new ArrayList<>(path));
        }
        if(start == nums.length){
            return ;
        }
        HashSet<Integer> hs = new HashSet<>();
        for(int i = start; i < nums.length; i ++){
            if(hs.contains(nums[i])){
                continue;
            }
            if(path.size()>=1 && path.get(path.size()-1) > nums[i]){
                continue;
            }
            hs.add(nums[i]);
            path.add(nums[i]);
            fun(nums, i + 1);
            path.remove(path.size()-1);
        }
    }
}
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二、力扣47. 全排列 II

class Solution {
    List<List<Integer>> res = new ArrayList<>();
    List<Integer> path = new ArrayList<>();
    boolean[] flag;
    public List<List<Integer>> permuteUnique(int[] nums) {
        flag = new boolean[nums.length];
        Arrays.fill(flag,false);
        Arrays.sort(nums);
        fun(nums);
        return res;
    }
    public void fun(int[] nums){
        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] && !flag[i-1]){
                continue;
            }
            if(flag[i]==false){
                flag[i] = true;
                path.add(nums[i]);
                fun(nums);
                path.remove(path.size()-1);
                flag[i] = false;
            }
        }
    }
}
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三、力扣46. 全排列

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