GeezerVison

The World Wide Web, restored to 800 pixels of glory.

GeezerVison is showing leetcodejavascript.com — #31 - Next Permutation - LeetCode JavaScript Solutions

Back to all solutions

#31 - Next Permutation

Medium • View on LeetCode • View on GitHub

Array Two Pointers

Problem Description

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

If such an arrangement is not possible, it must rearrange it as the lowest possible order (i.e., sorted in ascending order).

The replacement must be in place and use only constant extra memory.

Solution

/**
 * @param {number[]} nums
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var nextPermutation = function(nums) {
  let i = nums.length - 2;

  while (i >= 0 && nums[i + 1] <= nums[i]) {
    i--;
  }

  if (i >= 0) {
    let cursor = nums.length - 1;
    while (nums[cursor] <= nums[i]) {
      cursor--;
    }
    swap(nums, i, cursor);
  }

  reverse(nums, i + 1);
};

function reverse(nums, start) {
  let i = start;
  let j = nums.length - 1;

  while (i < j) {
    swap(nums, i, j);
    i++;
    j--;
  }
}

function swap(nums, i, j) {
  const temp = nums[i];
  nums[i] = nums[j];
  nums[j] = temp;
}

You are visitor 01402520 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.