1
/**
2
 * @param {number[]} nums
3
 * @return {number[][]}
4
 */
5
var permute = function (nums) {
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  const result = [];
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  const backtrack = (nums, path) => {
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    if (nums.length === 0) {
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      result.push(path);
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      return;
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    }
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    for (let i = 0; i < nums.length; i++) {
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      backtrack(
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        [...nums.slice(0, i), ...nums.slice(i + 1)],
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        [...path, nums[i]]
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      );
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    }
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  };
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  backtrack(nums, []);
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  return result;
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};