leetcode note--leetcode 75 Sort Colors

75. Sort Colors

 

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• Total Accepted: 130857
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• Difficulty: Medium
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Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.

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

Note:

You are not suppose to use the library's sort function for this problem.

第一种方法：自己写的，好理解

public class Solution {    public void sortColors(int[] nums) {        int len = nums.length;        int sorted = 0;        int p = 0;        for(int i = 0;i<2;i++){            p = sorted;            while(p<len){                if(nums[p]==i){                    if(nums[sorted]!=i){                        int tem = nums[p];                        nums[p] = nums[sorted];                        nums[sorted] = tem;                    }                    sorted++;                }                p++;            }        }    }}

time=1ms;

第二种方法：只做一次循环，原则只有一个，碰见0就往前扔，碰见2就往后扔；换完一次后，还要做二次判断，判断换过来的是几。

public class Solution {    public void sortColors(int[] nums) {      int len = nums.length;if(len==0 || len ==1) return;        int i = 0;//指向第一个不为0的数        int j = len-1;//从后边数，指向第一个不为2的数        int k = 1;        int tem;       /* while(i<len && nums[i]==0)i++;        while(j>=0 && nums[j]==2)j--;*/        k = i;        while(k<=j){        if(nums[k]==0){        tem = nums[i];        nums[i] = nums[k];        nums[k] = tem;        i++;        }        if(nums[k]==2){        tem = nums[j];        nums[j] = nums[k];        nums[k] = tem;        j--;        }else{        k++;        }        }    }}

time=0ms;