Add: Exercise 735. Asteroid Collision

Author: BlackBeast593

735-asteroid-collision/README.md

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+# 735. Asteroid Collision
+We are given an array `asteroids` of integers 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.
+
+## Examples
+
+### Example 1:
+
+Input: `asteroids` = [5,10,-5]  
+Output: [5,10]  
+Explanation: The 10 and -5 collide resulting in 10. The 5 and 10 never collide.
+
+### Example 2:
+
+Input: `asteroids` = [8,-8]  
+Output: []  
+Explanation: The 8 and -8 collide exploding each other.
+
+### Example 3:
+
+Input: `asteroids` = [10,2,-5]  
+Output: [10]  
+Explanation: The 2 and -5 collide resulting in -5. The 10 and -5 collide resulting in 10.
+
+## Constraints
+
+- 2 <= `asteroids.length` <= 10^4
+- -1000 <= `asteroids[i]` <= 1000
+- `asteroids[i]` != 0

735-asteroid-collision/index.js

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+/**
+ * @param {number[]} asteroids
+ * @return {number[]}
+ */
+var asteroidCollision = function(asteroids) {
+    const asteroidsStack = [asteroids[0]];
+    asteroidsStack.peek = () => asteroidsStack[asteroidsStack.length - 1];
+
+    let i = 1;
+    while (i < asteroids.length) {
+        // Detect collisions
+        // If two asteroids meet, the smaller one (by absolute value) will explode
+        if (asteroidsStack.peek() > 0 && asteroids[i] < 0) {
+            // Iterate until all collisions are resolved
+            while (asteroidsStack.peek() > 0 && asteroids[i] < 0) {
+                // If both are the same size (by absolute value), both will explode
+                if (asteroidsStack.peek() + asteroids[i] === 0) {
+                    asteroidsStack.pop();
+                    i++;
+                // If the incoming asteroid is larger (moving to the left), remove the top of the stack
+                } else if (asteroidsStack.peek() + asteroids[i] < 0) {
+                    asteroidsStack.pop();
+                // If the asteroid in the stack is larger (moving to the right), ignore the incoming asteroid
+                } else {
+                    i++;
+                }
+            }
+        // If there's no collision, add the asteroid to the stack
+        } else {
+            asteroidsStack.push(asteroids[i]);
+            i++;
+        }
+    }
+
+    delete asteroidsStack.peek
+    
+    return asteroidsStack;
+};
+
+module.exports = asteroidCollision

735-asteroid-collision/package.json

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+{
+  "name": "735-asteroid-collision",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js",
+    "debug": "node --inspect-brk index.js",
+    "test": "node test.js"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

735-asteroid-collision/test.js

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+const assert = require('assert')
+const asteroidCollision = require('./index')
+
+const tests = [
+    {
+        asteroids: [5,10,-5],
+        expectedOutput: [5,10]
+    },
+    {
+        asteroids: [8,-8],
+        expectedOutput: []
+    },
+    {
+        asteroids: [10,2,-5],
+        expectedOutput: [10]
+    },
+]
+
+for (const t of tests) {
+    assert.strict.deepEqual(asteroidCollision(t.asteroids), t.expectedOutput)
+}