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735. Asteroid Collision #67
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46 changes: 46 additions & 0 deletions
src/0735_asteroid_collision/ac.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,46 @@ | ||
| /* | ||
| 735. Asteroid Collision | ||
| https://leetcode.com/problems/asteroid-collision/ | ||
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| We are given an array asteroids of integers representing asteroids in a row. | ||
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| For each asteroid, the absolute value represents its size, | ||
| and the sign represents its direction (positive meaning right, negative meaning left). | ||
| Each asteroid moves at the same speed. | ||
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| Find out the state of the asteroids after all collisions. | ||
| If two asteroids meet, the smaller one will explode. If both are the same size, both will explode. | ||
| Two asteroids moving in the same direction will never meet. | ||
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| Note: | ||
| The length of asteroids will be at most 10000. | ||
| Each asteroid will be a non-zero integer in the range [-1000, 1000].. | ||
| */ | ||
| // time: 2019年01月14日 | ||
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| package ac | ||
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| // stack | ||
| // time complexity: O(N), where NN is the number of asteroids. Our stack pushes and pops each asteroid at most once. | ||
| // space complexity: O(N), the size of stack. | ||
| func asteroidCollision(asteroids []int) []int { | ||
| stack := make([]int, 0) | ||
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| for _, asteroid := range asteroids { | ||
| flag := true | ||
| for len(stack) > 0 && asteroid < 0 && stack[len(stack)-1] > 0 { | ||
| if stack[len(stack)-1] == -asteroid { | ||
| stack = stack[:len(stack)-1] | ||
| } else if stack[len(stack)-1] < -asteroid { | ||
| stack = stack[:len(stack)-1] | ||
| continue | ||
| } | ||
| flag = false | ||
| break | ||
| } | ||
| if flag { | ||
| stack = append(stack, asteroid) | ||
| } | ||
| } | ||
| return stack | ||
| } |
30 changes: 30 additions & 0 deletions
src/0735_asteroid_collision/ac_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| package ac | ||
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| import ( | ||
| "reflect" | ||
| "testing" | ||
| ) | ||
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| func TestAsteroidCollision(t *testing.T) { | ||
| testCases := [][]int{ | ||
| {5, 10, -5}, | ||
| {-2, 2, -1, -2}, | ||
| {-2, -1, 1, 2}, | ||
| {8, -8}, | ||
| {10, 2, -5}, | ||
| } | ||
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| expected := [][]int{ | ||
| {5, 10}, | ||
| {-2}, | ||
| {-2, -1, 1, 2}, | ||
| {}, | ||
| {10}, | ||
| } | ||
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| for index, asteroids := range testCases { | ||
| if res := asteroidCollision(asteroids); !reflect.DeepEqual(res, expected[index]) { | ||
| t.Errorf("expected %v, got %v", expected[index], res) | ||
| } | ||
| } | ||
| } |
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