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.
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?
1 /************************************************************************* 2 > File Name: LeetCode075.c 3 > Author: Juntaran 4 > Mail: JuntaranMail@gmail.com 5 > Created Time: Tue 19 May 2016 20:41:54 PM CST 6 ************************************************************************/ 7 8 /************************************************************************* 9 10 Sort Colors 11 12 Given an array with n objects colored red, white or blue, 13 sort them so that objects of the same color are adjacent, 14 with the colors in the order red, white and blue. 15 16 Here, we will use the integers 0, 1, and 2 to represent the color red, 17 white, and blue respectively. 18 19 Note: 20 You are not suppose to use the library's sort function for this problem. 21 22 click to show follow up. 23 24 Follow up: 25 A rather straight forward solution is a two-pass algorithm 26 using counting sort. 27 First, iterate the array counting number of 0's, 1's, and 2's, 28 then overwrite array with total number of 0's, then 1's and followed by 2's. 29 30 Could you come up with an one-pass algorithm using only constant space? 31 32 ************************************************************************/ 33 34 #include <stdio.h> 35 #include <stdlib.h> 36 37 void printNums(int* nums, int numsSize) 38 { 39 int i; 40 for( i=0; i<numsSize; i++ ) 41 { 42 printf("%d ",nums[i]); 43 } 44 printf(" "); 45 } 46 47 /* 高端做法 */ 48 void sortColors(int* nums, int numsSize) 49 { 50 int red=-1, white=-1, blue=-1; 51 int i; 52 53 printNums(nums, numsSize); 54 for( i=0; i<numsSize; i++ ) 55 { 56 if(nums[i] == 0) 57 { 58 nums[++blue] =2; 59 nums[++white]=1; 60 nums[++red] =0; 61 printNums(nums, numsSize); 62 } 63 else if (nums[i] == 1) 64 { 65 nums[++blue] =2; 66 nums[++white]=1; 67 printNums(nums, numsSize); 68 69 } 70 else if (nums[i] == 2) 71 { 72 nums[++blue] =2; 73 printNums(nums, numsSize); 74 } 75 } 76 } 77 78 79 /* 80 81 ------- Before meeting nums[3] ------- 82 index: 0 1 2 3 4 5 6 7 8 83 nums: 0 1 2 1 2 0 2 2 1 84 lables: r w b 85 86 paint: 2 2 2 87 1 1 88 0 89 90 appear: 0 1 2 91 92 ------- After dealing with nums[3] ------- 93 index: 0 1 2 3 4 5 6 7 8 94 nums: 0 1 2 1 2 0 2 2 1 95 lables: r w b 96 97 paint: 2 2 2 2 98 1 1 1 99 0 100 101 appear: 0 1 1 2 102 103 ------- After finish iteration ------- 104 index: 0 1 2 3 4 5 6 7 8 105 nums: 0 1 2 1 2 0 2 2 1 106 lables: r w b 107 108 paint: 2 2 2 2 2 2 2 2 2 109 1 1 1 1 1 110 0 0 111 112 appear: 0 0 1 1 1 2 2 2 2 113 114 */ 115 116 117 /* 智障做法 */ 118 void sortColors2(int* nums, int numsSize) 119 { 120 int red = 0; 121 int white = 0; 122 int blue = 0; 123 124 int i; 125 for( i=0; i<numsSize; i++ ) 126 { 127 if( nums[i] == 0 ) 128 { 129 red ++; 130 } 131 if( nums[i] == 1 ) 132 { 133 white ++; 134 } 135 if( nums[i] == 2 ) 136 { 137 blue ++; 138 } 139 } 140 // printf("%d %d %d ", red,white,blue); 141 142 for( i=0; i<red; i++ ) 143 { 144 nums[i] = 0; 145 } 146 // printNums(nums, numsSize); 147 148 for( i=red; i<white+red; i++ ) 149 { 150 nums[i] = 1; 151 } 152 // printNums(nums, numsSize); 153 154 for( i=white+red; i<white+red+blue; i++ ) 155 { 156 nums[i] = 2; 157 } 158 // printNums(nums, numsSize); 159 } 160 161 162 163 int main() 164 { 165 int nums[] = {1,0,1,2,1,0,2,0,2}; 166 int numsSize = 9; 167 sortColors(nums, numsSize); 168 169 return 0; 170 }