|
| 1 | +#defineINIT_HASH_SIZE 4096 |
| 2 | + |
| 3 | +// Represent an element in a hash table. |
| 4 | +typedefstructHash { |
| 5 | +intkey; |
| 6 | +structHash*next; |
| 7 | +}Hash; |
| 8 | + |
| 9 | +Hash**InitHash() { |
| 10 | +Hash**h= (Hash**)calloc(INIT_HASH_SIZE,sizeof(Hash*)); |
| 11 | +assert(h); |
| 12 | +returnh; |
| 13 | +} |
| 14 | + |
| 15 | +Hash*NewHash(intkey) { |
| 16 | +Hash*h= (Hash*)malloc(sizeof(Hash)); |
| 17 | +assert(h); |
| 18 | +h->key=key; |
| 19 | +h->next=NULL; |
| 20 | +returnh; |
| 21 | +} |
| 22 | + |
| 23 | +intHashKey(intkey) { |
| 24 | +while(key<0)key+=INIT_HASH_SIZE; |
| 25 | +return (key %INIT_HASH_SIZE); |
| 26 | +} |
| 27 | + |
| 28 | +voidAddHash(Hash**hash,intkey) { |
| 29 | +assert(hash); |
| 30 | +inthash_key=HashKey(key); |
| 31 | +Hash**head=hash+hash_key; |
| 32 | +if (!*head) { |
| 33 | +*head=NewHash(key); |
| 34 | + }else { |
| 35 | +Hash*h=*head; |
| 36 | +while (h) { |
| 37 | +if (h->key==key) { |
| 38 | +return; |
| 39 | + }elseif (!h->next) { |
| 40 | +h->next=NewHash(key); |
| 41 | +return; |
| 42 | + } |
| 43 | +h=h->next; |
| 44 | + } |
| 45 | + } |
| 46 | +} |
| 47 | + |
| 48 | +// If hash not round return 0 on purpose. |
| 49 | +intGetHash(Hash**hash,intkey) { |
| 50 | +assert(hash); |
| 51 | +Hash*h=hash[HashKey(key)]; |
| 52 | +while(h) { |
| 53 | +if (h->key==key) { |
| 54 | +return1; |
| 55 | + } |
| 56 | +h=h->next; |
| 57 | + } |
| 58 | + |
| 59 | +return0; |
| 60 | +} |
| 61 | + |
| 62 | +intlongestConsecutive(int*nums,intnumsSize){ |
| 63 | +Hash**hash=InitHash(); |
| 64 | +inti,len,n,maxLen=0; |
| 65 | + |
| 66 | +for (i=0;i<numsSize;i++) { |
| 67 | +AddHash(hash,nums[i]); |
| 68 | + } |
| 69 | +for (i=0;i<numsSize;i++) { |
| 70 | +n=nums[i]; |
| 71 | +len=1; |
| 72 | +if (GetHash(hash,n-1)==0) { |
| 73 | +while(GetHash(hash,++n)==1) { |
| 74 | +len++; |
| 75 | + } |
| 76 | + } |
| 77 | +maxLen= (len>maxLen) ?len :maxLen; |
| 78 | + } |
| 79 | + |
| 80 | +returnmaxLen; |
| 81 | +} |
| 82 | + |
| 83 | +// |
| 84 | +// According to the official solution, using hash map will be considered as O(n). |
| 85 | +// |
| 86 | +// Alternative solution 1 - With uthash, the runtime is poorer. It is a little surprise. |
| 87 | +// |
| 88 | +// typedef struct Hash { |
| 89 | +// int num; |
| 90 | +// UT_hash_handle hh; |
| 91 | +// } Hash; |
| 92 | +// |
| 93 | +// void AddHash(Hash **hash, int num) { |
| 94 | +// Hash *entry; |
| 95 | +// HASH_FIND_INT(*hash, &num, entry); |
| 96 | +// if (!entry) { |
| 97 | +// entry = malloc(sizeof(Hash)); |
| 98 | +// entry->num = num; |
| 99 | +// HASH_ADD_INT(*hash, num, entry); |
| 100 | +// } |
| 101 | +// } |
| 102 | +// |
| 103 | +// Hash * GetHash(Hash **hash, int num) { |
| 104 | +// Hash *entry = NULL; |
| 105 | +// HASH_FIND_INT(*hash, &num, entry); |
| 106 | +// return entry; |
| 107 | +// } |
| 108 | +// |
| 109 | +// int longestConsecutive(int* nums, int numsSize){ |
| 110 | +// Hash *root = NULL; |
| 111 | +// int i, len, n, maxLen = 0; |
| 112 | +// |
| 113 | +// for (i = 0; i < numsSize; i++) { |
| 114 | +// AddHash(&root, nums[i]); |
| 115 | +// } |
| 116 | +// for (i = 0; i < numsSize; i++) { |
| 117 | +// n = nums[i]; |
| 118 | +// len = 1; |
| 119 | +// if (!GetHash(&root, n - 1)) { |
| 120 | +// while(GetHash(&root, ++n)) { |
| 121 | +// len++; |
| 122 | +// } |
| 123 | +// } |
| 124 | +// maxLen = (len > maxLen) ? len : maxLen; |
| 125 | +// } |
| 126 | +// |
| 127 | +// return maxLen; |
| 128 | +// } |
| 129 | +// |
| 130 | +// |
| 131 | +// Alternative solution 2 - With sorting, O(nlogn), the runtime is the best. |
| 132 | +// |
| 133 | +// int compare(const void *a, const void *b) { |
| 134 | +// return *(int*)a - *(int*)b; |
| 135 | +// } |
| 136 | +// |
| 137 | +// int longestConsecutive(int* nums, int numsSize){ |
| 138 | +// int i, len, max; |
| 139 | +// if (numsSize <= 0) { |
| 140 | +// return 0; |
| 141 | +// } |
| 142 | +// len = 1; |
| 143 | +// max = 1; |
| 144 | +// qsort(nums, numsSize, sizeof(int), compare); |
| 145 | +// for (i = 0; i < numsSize - 1; i++) { |
| 146 | +// if (nums[i] + 1 == nums[i + 1]) { |
| 147 | +// len++; |
| 148 | +// } else if (nums[i] == nums[i + 1]){ |
| 149 | +// continue; |
| 150 | +// } else { |
| 151 | +// len = 1; |
| 152 | +// } |
| 153 | +// max = (max > len) ? max : len; |
| 154 | +// } |
| 155 | +// |
| 156 | +// return max; |
| 157 | +// } |
| 158 | +// |