Sort Colors

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.

解题思路：首先，题目要求按顺序排列0，1，2三个数字。当按顺序排列2个数字时，较容易解决；按这个思路来的话,将数组分为两个堆栈，一旦遇到2就将其置于数组尾部的栈；遍历搜索整个数组，当搜索至存放2的栈顶时退出;

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

void sortColors(int A[], int n) {
	int stackIdx_blue = n - 1;
	int stackIdx_red = 0;

	for (int i = 0; i <= stackIdx_blue;)
	{
		if (A[i] == 2){
			swap(A[i], A[stackIdx_blue]);
			stackIdx_blue--;
		}
		else if (A[i] == 0){
			swap(A[i], A[stackIdx_red]);
			stackIdx_red++;
			++i;
		}
		else
			++i;
	}
}