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47. 全排列 II

给定一个可包含重复数字的序列 nums ,按任意顺序 返回所有不重复的全排列

示例 1:
输入:nums = [1,1,2]
输出:
[[1,1,2],
[1,2,1],
[2,1,1]]

示例 2:
输入:nums = [1,2,3]
输出:[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

提示:
1 <= nums.length <= 8
-10 <= nums[i] <= 10

javascript
/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var permuteUnique = function (nums) {
  const res = []
  const vis = Array.from({ length: nums.length }, () => false)
  const backtrack = (idx, perm) => {
    if (idx === nums.length) {
      res.push(perm.slice())
      return
    }
    for (let i = 0; i < nums.length; ++i) {
      if (vis[i] || (i > 0 && nums[i] === nums[i - 1] && !vis[i - 1])) {
        continue
      }
      perm.push(nums[i])
      vis[i] = true
      backtrack(idx + 1, perm)
      vis[i] = false
      perm.pop()
    }
  }
  nums.sort((a, b) => a - b)
  backtrack(0, [])
  return res
}

console.log(permuteUnique([1, 1, 2]))
console.log(permuteUnique([1, 2, 3]))