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sortColors.cpp
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76 lines (65 loc) · 1.78 KB
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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;
}