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75-Sort-Colors.md

问题描述

Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

Example 1:

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Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Example 2:

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Input: nums = [2,0,1]
Output: [0,1,2]

Example 3:

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Input: nums = [0]
Output: [0]

Example 4:

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Input: nums = [1]
Output: [1]

Constraints:

  • n == nums.length
  • 1 <= n <= 300
  • nums[i] is 0, 1, or 2.

Follow up:

  • Could you solve this problem without using the library’s sort function?
  • Could you come up with a one-pass algorithm using only O(1) constant space?

解题思路

  • 分为0,1,2三种情况,0从memo的头部插入,1从memo尾部插入,同时都将这几个元素从nums中删除
  • 最后将memo和nums组合起来即可
  • 代码如下:

  • JavaScript

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/**
* @param {number[]} nums
* @return {void} Do not return anything, modify nums in-place instead.
*/
var sortColors = function(nums) {
var i = 0;
var memo = [];

while (i < nums.length) {
switch(nums[i]) {
case 0:
memo.unshift(...nums.splice(i, 1));
break;
case 1:
memo.push(...nums.splice(i, 1));
break;
default:
i++;
break;
}
}

nums.unshift(...memo);
};
  • 时间复杂度:O(n)
  • 空间复杂度:O(n)