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1 | 1 | /** |
2 | | - * Note: Array must be sorted for binary search |
| 2 | + * Note: Array must be sorted for ternary search |
3 | 3 | * Complexity: |
4 | 4 | * Worst case time complexity: O(log N) |
5 | 5 | * Average case time complexity: O(log N) |
6 | 6 | * Best case time complexity: O(1) |
7 | 7 | * Space complexity: O(1) |
8 | 8 | */ |
9 | 9 | function ternarySearch(arr, key){ |
10 | | - let left = 0; |
11 | | - let right = arr.length - 1; |
12 | | - while(left <= right){ |
13 | | - let temp2 = left + Math.floor((right - left) / 3); |
14 | | - let temp3 = left + 2 * Math.floor((right - left) / 3); |
15 | | - if(key == arr[left]){ |
16 | | - return left; |
17 | | - } else if(key == arr[right]){ |
18 | | - return right; |
19 | | - } else if(key < arr[left] || key > arr[right]){ |
20 | | - return null; |
21 | | - } else if(key <= arr[temp2]){ |
22 | | - right = temp2; |
23 | | - } else if(key > arr[temp2] && key <= arr[temp3]){ |
24 | | - left = temp2 + 1; |
25 | | - right = temp3; |
| 10 | + let low = 0; |
| 11 | + let high = arr.length - 1; |
| 12 | + while(low <= high){ |
| 13 | + let lowMiddle = low + Math.floor((high - low) / 3); |
| 14 | + let highMiddle = low + 2 * Math.floor((high - low) / 3); |
| 15 | + if(key == arr[low]){ |
| 16 | + return low; |
| 17 | + } else if(key == arr[high]){ |
| 18 | + return high; |
| 19 | + } else if(key <= arr[lowMiddle]){ |
| 20 | + high = lowMiddle; |
| 21 | + } else if(key > arr[lowMiddle] && key <= arr[highMiddle]){ |
| 22 | + low = lowMiddle + 1; |
| 23 | + high = highMiddle; |
26 | 24 | } else { |
27 | | - left = temp3 + 1; |
| 25 | + low = highMiddle + 1; |
28 | 26 | } |
29 | 27 | } |
30 | 28 | return null; |
31 | 29 | } |
32 | 30 |
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33 | 31 | function ternarySearchRecursive(arr, low, high, key){ |
34 | | - |
35 | | - if(high >= low){ |
| 32 | + if(high > low){ |
36 | 33 | let highMiddle = low + 2 * Math.floor((high - low) / 3); |
37 | 34 | let lowMiddle = low + Math.floor((high - low) / 3); |
38 | 35 | if(key === arr[lowMiddle]){ |
39 | 36 | return lowMiddle; |
40 | 37 | } else if(key === arr[highMiddle]){ |
41 | 38 | return highMiddle; |
42 | | - } else if(key < arr[highMiddle]){ |
43 | | - return ternarySearchRecursive(arr, low, lowMiddle, key); |
| 39 | + } else if(key === arr[high]){ |
| 40 | + return high; |
| 41 | + } else if(key < arr[lowMiddle]){ |
| 42 | + return ternarySearchRecursive(arr, low, lowMiddle - 1, key); |
44 | 43 | } else if(key > arr[lowMiddle] && key < arr[highMiddle]){ |
45 | | - return ternarySearchRecursive(arr, lowMiddle, highMiddle, key); |
46 | | - } else if(arr.indexOf(key) == - 1){ |
47 | | - return null; |
| 44 | + return ternarySearchRecursive(arr, lowMiddle + 1, highMiddle - 1, key); |
48 | 45 | } else { |
49 | | - return ternarySearchRecursive(arr, highMiddle, high, key); |
| 46 | + return ternarySearchRecursive(arr, highMiddle+1, high, key); |
50 | 47 | } |
51 | 48 | } |
52 | 49 | return null; |
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