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Diffstat (limited to 'asteroid_collision.cpp')
-rw-r--r-- | asteroid_collision.cpp | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/asteroid_collision.cpp b/asteroid_collision.cpp new file mode 100644 index 0000000..3597c8a --- /dev/null +++ b/asteroid_collision.cpp @@ -0,0 +1,52 @@ +// 735. Asteroid Collision +#include "leetcode.h" + +/* + * given an array 'asteroids' o intergers representing asteroids in a row. 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. 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. + */ + +class Solution { +public: + vector<int> asteroidCollision(vector<int> &asteroids) { + int n = asteroids.size(); + stack<int> s; + for (int i = 0; i < n; i++) { + if (asteroids[i] || s.empty()) + s.push(asteroids[i]); + else { + while (!s.empty() && s.top() && s.top() < abs(asteroids[i])) + s.pop(); + if (!s.empty() && s.top() == abs(asteroids[i])) + s.pop(); + else if (s.empty() || s.top() < 0) + s.push(asteroids[i]); + } + } + vector<int> ans(s.size()); + for (int i = (int)s.size() - 1; i >= 0; i--) { + ans[i] = s.top(); + s.pop(); + } + return ans; + } +}; + +int main() { + Solution obj; + vector<int> a1 = {5, 10, -5}, a2 = {8, -8}, a3 = {10, 2, -5}; + for (auto i : obj.asteroidCollision(a1)) + printf("%d ", i); // expect: 5 10 + printf("\n"); + for (auto i : obj.asteroidCollision(a2)) + printf("%d ", i); // expect: nil + printf("\n"); + for (auto i : obj.asteroidCollision(a3)) + printf("%d ", i); // expect: 10 + printf("\n"); +} |