Created
April 26, 2012 01:54
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Search in a sorted, rotated list. Given a sorted list of N integers that has been rotated an unknown number of positions, e.g., 15 36 1 7 12 13 14, design an O(log N) algorithm to determine if a given integer is in the list.
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| def search_arr arr,val | |
| darr = arr+arr | |
| sz = arr.size | |
| start_loc = 0 | |
| end_loc = sz - 1 | |
| mid_loc = (end_loc - start_loc)/2 | |
| while start_loc < end_loc | |
| return true if arr[mid_loc] == val | |
| if arr[start_loc] < arr[mid_loc] | |
| if arr[start_loc] <= val and val <= arr[mid_loc] | |
| end_loc = mid_loc | |
| mid_loc = start_loc + (end_loc - start_loc) /2 | |
| else | |
| start_loc = mid_loc + 1 | |
| mid_loc = start_loc + (end_loc - start_loc)/2 | |
| end | |
| else | |
| if arr[mid_loc] <= val and val <= arr[end_loc] | |
| start_loc = mid_loc | |
| mid_loc = start_loc + (end_loc - start_loc)/2 | |
| else | |
| start_loc = mid_loc + 1 | |
| mid_loc = start_loc + (end_loc - start_loc)/2 | |
| end | |
| end | |
| end | |
| return false | |
| end |
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