LeetCode 229

 1 /*************************************************************************
 2     > File Name: LeetCode229.c
 3     > Author: Juntaran
 4     > Mail: Juntaranmail@gmail.com
 5     > Created Time: Tue 13 May 2016 15:02:25 PM CST
 6  ************************************************************************/
 7  
 8 /*************************************************************************
 9 
10     Majority Element II
11     
12     Given an integer array of size n, 
13     find all elements that appear more than ⌊ n/3 ⌋ times. 
14     The algorithm should run in linear time and in O(1) space.
15 
16     Hint:
17 
18     How many majority elements could it possibly have?
19     Do you have a better hint? Suggest it!
20 
21  ************************************************************************/
22 
23 #include<stdio.h>
24 
25 /**
26  * Return an array of size *returnSize.
27  * Note: The returned array must be malloced, assume caller calls free().
28  */
29  
30 int* majorityElement(int* nums, int numsSize, int* returnSize)
31 {
32     int firstMajor = 0, count1 = 0, secondMajor = 0, count2 = 0, i = 0;
33     *returnSize = 0;
34 
35     for (i = 0; i < numsSize; i++)
36     {
37         if (count1 == 0) firstMajor = nums[i];
38         else if (count2 == 0 && firstMajor != nums[i]) secondMajor = nums[i];
39 
40         if (nums[i] == firstMajor)
41             count1++;
42         else if (nums[i] == secondMajor)
43             count2++;
44         else
45             count1--, count2--;
46     }
47     count1 = count2 = 0;
48     for (i = 0; i < numsSize; i++)
49     {
50         if (nums[i] == firstMajor) count1++;
51         else if (nums[i] == secondMajor) count2++;
52     }
53     if (count1 > numsSize / 3)
54         (*returnSize)++;
55     else
56         firstMajor = secondMajor;
57     if (count2 > numsSize / 3)
58         (*returnSize)++;
59 
60     if (*returnSize == 0) return NULL;
61     int *returnArray = (int *)malloc(sizeof(int) * (*returnSize));
62     if (returnArray != NULL)
63     {
64         returnArray[0] = firstMajor;
65         if (*returnSize > 1) returnArray[1] = secondMajor;
66     }
67 
68     return returnArray;
69 }
70 
71 int main()
72 {
73     int nums[] = {2,2,1};
74     int numsSize = 3;
75     int *returnSize = 0;
76     majorityElement( nums, numsSize, *returnSize);
77 
78     return 0;
79 }