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find first and last position of element in sorted array #6
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find-first-and-last-position-of-element-in-sorted-array
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139 changes: 139 additions & 0 deletions
...ion_of_element_in_sorted_array/find_first_and_last_position_of_element_in_sorted_array.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| /* | ||
| 34. Find First and Last Position of Element in Sorted Array | ||
| https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/ | ||
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| Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value. | ||
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| Your algorithm's runtime complexity must be in the order of O(log n). | ||
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| If the target is not found in the array, return [-1, -1]. | ||
| */ | ||
| // time: 2018年12月20日 | ||
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| package findfirstandlastpositionofelementinsortedarray | ||
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| // binary search | ||
| // time complexity: O(logn) | ||
| // space complexity: O(1) | ||
| func searchRange(nums []int, target int) []int { | ||
| lowerIndex := firstOccurance(nums, target) | ||
| first := -1 | ||
| if lowerIndex != len(nums) && target == nums[lowerIndex] { | ||
| first = lowerIndex | ||
| } | ||
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| upperIndex := lastOccurance(nums, target) | ||
| last := -1 | ||
| if upperIndex == len(nums) && len(nums) > 0 && target == nums[len(nums)-1] { | ||
| last = len(nums) - 1 | ||
| } else if upperIndex != len(nums) && upperIndex > 0 && target == nums[upperIndex-1] { | ||
| last = upperIndex - 1 | ||
| } | ||
| return []int{first, last} | ||
| } | ||
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| func firstOccurance(nums []int, target int) int { | ||
| var ( | ||
| l int | ||
| r = len(nums) | ||
| ) | ||
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| for l != r { // 夹逼思想 | ||
| mid := l + (r-l)/2 | ||
| if nums[mid] < target { | ||
| l = mid + 1 | ||
| } else { | ||
| r = mid | ||
| } | ||
| } | ||
| return l | ||
| } | ||
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| func lastOccurance(nums []int, target int) int { | ||
| var ( | ||
| l int | ||
| r = len(nums) | ||
| ) | ||
| for l != r { | ||
| mid := l + (r-l)/2 | ||
| if nums[mid] <= target { | ||
| l = mid + 1 | ||
| } else { | ||
| r = mid | ||
| } | ||
| } | ||
| return l | ||
| } | ||
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| // double index scan | ||
| // Time complexity: O(n) | ||
| // Space complexity: O(1) | ||
| func searchRange1(nums []int, target int) []int { | ||
| var ( | ||
| l int | ||
| r = len(nums) - 1 | ||
| ) | ||
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| for l <= r { | ||
| flag := false | ||
| if nums[l] != target { | ||
| l++ | ||
| flag = true | ||
| } | ||
| if nums[r] != target { | ||
| r-- | ||
| flag = true | ||
| } | ||
| if !flag { | ||
| break | ||
| } | ||
| } | ||
| if r < l { | ||
| return []int{-1, -1} | ||
| } | ||
| return []int{l, r} | ||
| } | ||
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| // binary search + linear scan | ||
| // Time complexity: O(logn) ~ O(n) | ||
| // Space complexity: O(1) | ||
| func searchRange2(nums []int, target int) []int { | ||
| var ( | ||
| l int | ||
| r = len(nums) - 1 | ||
| tmp = -1 | ||
| ) | ||
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| for l <= r { | ||
| mid := l + (r-l)/2 | ||
| if nums[mid] == target { | ||
| tmp = mid | ||
| break | ||
| } | ||
| if nums[mid] < target { | ||
| l = mid + 1 | ||
| } else { | ||
| r = mid - 1 | ||
| } | ||
| } | ||
| if -1 == tmp { | ||
| return []int{-1, -1} | ||
| } | ||
| l = tmp | ||
| r = tmp | ||
| for true { | ||
| if l > 0 && nums[l-1] == target { | ||
| l-- | ||
| } else { | ||
| break | ||
| } | ||
| } | ||
| for true { | ||
| if r < len(nums)-1 && target == nums[r+1] { | ||
| r++ | ||
| } else { | ||
| break | ||
| } | ||
| } | ||
| return []int{l, r} | ||
| } |
64 changes: 64 additions & 0 deletions
...f_element_in_sorted_array/find_first_and_last_position_of_element_in_sorted_array_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,64 @@ | ||
| package findfirstandlastpositionofelementinsortedarray | ||
|
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| import ( | ||
| "reflect" | ||
| "runtime" | ||
| "testing" | ||
| ) | ||
|
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| func TestSearchRange(t *testing.T) { | ||
| type arg struct { | ||
| nums []int | ||
| target int | ||
| } | ||
|
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| testCases := []arg{ | ||
| arg{ | ||
| nums: []int{5, 7, 7, 8, 8, 10}, | ||
| target: 8, | ||
| }, | ||
| arg{ | ||
| nums: []int{5, 7, 7, 8, 8, 10}, | ||
| target: 6, | ||
| }, | ||
| arg{ | ||
| nums: []int{1}, | ||
| target: 1, | ||
| }, | ||
| arg{ | ||
| nums: []int{}, | ||
| target: 0, | ||
| }, | ||
| arg{ | ||
| nums: []int{2, 2}, | ||
| target: 2, | ||
| }, | ||
| arg{ | ||
| nums: []int{1}, | ||
| target: 0, | ||
| }, | ||
| } | ||
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| expected := [][]int{ | ||
| {3, 4}, | ||
| {-1, -1}, | ||
| {0, 0}, | ||
| {-1, -1}, | ||
| {0, 1}, | ||
| {-1, -1}, | ||
| } | ||
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| testFuncs := []func([]int, int) []int{ | ||
| searchRange, | ||
| searchRange1, | ||
| searchRange2, | ||
| } | ||
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| for _, testFunc := range testFuncs { | ||
| for index, testData := range testCases { | ||
| if res := testFunc(testData.nums, testData.target); !reflect.DeepEqual(res, expected[index]) { | ||
| t.Errorf("function %s, expected %v, got %v", runtime.FuncForPC(reflect.ValueOf(testFunc).Pointer()).Name(), expected[index], res) | ||
| } | ||
| } | ||
| } | ||
| } |
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69 changes: 69 additions & 0 deletions
utils/set_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,69 @@ | ||
| package utils | ||
|
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| import ( | ||
| "testing" | ||
| "unsafe" | ||
| ) | ||
|
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| func TestEmptyStruct(t *testing.T) { | ||
| if unsafe.Sizeof(Exists) != 0 { | ||
| t.Error("Exists size must be zero.") | ||
| } | ||
| } | ||
|
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| func TestContains(t *testing.T) { | ||
| set := NewSet(3, 4) | ||
| set.Add(5) | ||
| if set.Contains(3) != true { | ||
| t.Error("should contains 4.") | ||
| } | ||
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| if set.Contains(6) != false { | ||
| t.Error("should not contains 6.") | ||
| } | ||
| } | ||
|
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| func TestSize(t *testing.T) { | ||
| set := NewSet(3, 4) | ||
| set.Add(5) | ||
| if set.Size() != 3 { | ||
| t.Error("size should be 3.") | ||
| } | ||
| } | ||
|
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| func TestEqual(t *testing.T) { | ||
| set := NewSet(3, 4) | ||
| set.Add(5) | ||
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| set1 := NewSet(3, 4, 5) | ||
| if set.Equal(set1) != true { | ||
| t.Error("set should equal with set1.") | ||
| } | ||
| set1.Add(6) | ||
| if set.Equal(set1) == true { | ||
| t.Error("set shouldn't equal with set1.") | ||
| } | ||
| } | ||
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| func TestIsSubset(t *testing.T) { | ||
| set := NewSet(3, 4) | ||
| set.Add(5) | ||
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| set1 := NewSet(3, 4, 5, 6) | ||
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| if set1.IsSubset(set) == true { | ||
| t.Error("set1 shouldn't be set's subset.") | ||
| } | ||
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| if set.IsSubset(set1) == false { | ||
| t.Error("set should be set1's subset.") | ||
| } | ||
| } | ||
|
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| func TestClear(t *testing.T) { | ||
| set := NewSet(3, 4) | ||
| set.Clear() | ||
| if set.Size() != 0 { | ||
| t.Error("set should be clear.") | ||
| } | ||
| } |
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