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SortColors.h
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48 lines (44 loc) · 1.43 KB
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/**************************************
* Author : luoshikai
* Version : 1.0
* Date : 2013-10-22
* Email : [email protected]
*************************************/
/**************************************
* 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.
*
* click to show follow up.
*
* 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?
*************************************/
class Solution {
public:
void sortColors(int A[], int n)
{
int zeros = 0, ones = 0, twos = 0;
for (int i = 0; i < n; ++i)
{
if (A[i] == 0) zeros++;
if (A[i] == 1) ones++;
if (A[i] == 2) twos++;
}
int i = 0;
for (int j = 0; j < zeros; ++i, ++j) A[i] = 0;
for (int j = 0; j < ones; ++i, ++j) A[i] = 1;
for (int j = 0; j < twos; ++i, ++j) A[i] = 2;
}
};