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.
Follow up:
A rather straight forward solution is a two-pass algorithm using counting sort.
First, iterate the array counting number of 0‘s, 1‘s, and 2‘s, then overwrite array with total number of 0‘s, then 1‘s and followed by 2‘s.
Could you come up with an one-pass algorithm using only constant space?
对只有三种值0、1、2的数组进行排序，要求扫描一遍就排好序
排好序之后0在前，1在中，2在后
class Solution {
public:
void sortColors(int A[], int n) {
if(n==0 || n==1)return;
int p1=0, p2=n-1;
while(A[p1]==0)p1++;
while(A[p2]==2)p2--;
int p=p1;
while(p<=p2){
if(A[p]==0){
if(p==p1){p1++; p++;}
else{
A[p]=A[p1];
A[p1]=0;
while(A[p1]==0)p1++;
}
}
else if(A[p]==2){
if(p==p2)p++;
else{
A[p]=A[p2];
A[p2]=2;
while(A[p2]==2)p2--;
}
}
else p++;
}
}
};LeetCode: Sort Colors [075],布布扣,bubuko.com
原文：http://blog.csdn.net/harryhuang1990/article/details/27367189