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LC47_permutations_ii.java
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99 lines (84 loc) · 2.71 KB
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package Week03;
import java.util.*;
import java.util.stream.Collectors;
public class LC47_permutations_ii {
/*
* 先排序，有相同值跳过一个，把数组排列完再放入结果
* */
public List<List<Integer>> permuteUnique(int[] nums) {
List<List<Integer>> res = new ArrayList<>();
if (nums == null || nums.length == 0) {
return res;
}
Arrays.sort(nums);
backtrack(res, nums, 0);
return res;
}
private void backtrack(List<List<Integer>> res, int[] nums, int level) {
if (nums.length == level) {
res.add(Arrays.stream(nums).boxed().collect(Collectors.toList()));
return;
}
backtrack(res, nums, level + 1);
for (int i = 0; i < level; i++) {
//avoid duplicated,need to be break for the same value
if (nums[i] == nums[level]) {
break;
}
swap(nums, i, level);
backtrack(res, nums, level + 1);
swap(nums, i, level);
}
return;
}
private void swap(int[] nums, int i, int j) {
// must be value of i assign to j first
nums[i] = (nums[i] + nums[j]) - (nums[j] = nums[i]);
}
/*Solution2:
Bruit force*/
int length;
public List<List<Integer>> permuteUnique_1(int[] nums) {
List<List<Integer>> res = new ArrayList<>();
if (nums == null || nums.length == 0) {
return res;
}
length = nums.length;
List<Integer> list = new ArrayList<>();
Set<String> set = new HashSet<>();
boolean[] used = new boolean[length];
dps(res, nums, list, used, set);
return res;
}
private void dps(
List<List<Integer>> res, int[] nums, List<Integer> list, boolean[] used, Set<String> set) {
if (list.size() == length) {
StringBuilder sb = new StringBuilder();
for (Integer i : list) {
sb.append(i);
sb.append("-");
}
if (!set.contains(sb.toString())) {
res.add(new ArrayList(list));
set.add(sb.toString());
}
return;
}
for (int i = 0; i < length; i++) {
if (!used[i]) {
list.add(nums[i]);
used[i] = true;
dps(res, nums, list, used, set);
used[i] = false;
list.remove(list.size() - 1);
}
}
}
}
class Test {
public static void main(String[] args) {
int[] nums = new int[]{2, 2, 1, 1};
LC47_permutations_ii solution = new LC47_permutations_ii();
List<List<Integer>> res = solution.permuteUnique(nums);
}
}