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// Source : https://oj.leetcode.com/problems/sort-colors/

// Author : Hao Chen

// Date : 2014-06-25

/**********************************************************************************

*

* 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?

*

**********************************************************************************/

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

void swap(int*a, int*b)

{

int t;

t=*a;

*a = *b;

*b = t;

}

void sortColors(int a[], int n) {

int zero=0, two=n-1;

for(int i=0; i<=two; i++ ){

if (a[i]==0){

swap(&a[zero], &a[i]);

zero++;

}

if (a[i]==2){

swap(&a[two], &a[i]);

two--;

i--;

}

}

}

void printArray(int a[], int n) {

for(int i=0; i<n; i++){

printf("%d ", a[i]);

}

printf("\n");

}

int main(int argc, char** argv)

{

int n = 7;

if (argc>1)

n = atoi(argv[1]);

srand(time(NULL));

int *a = new int[n];

for (int i=0; i<n; i++){

a[i] = random()%3;

}

printArray(a, n);

sortColors(a, n);

printArray(a, n);

delete[] a;

}