Added 3Sum, Min Stack and SumOfSquare

Author: ignacio-chiazzo

LeetcodeProblems/3Sum.js

@@ -0,0 +1,60 @@
+/*
+3Sum
+https://leetcode.com/problems/3sum/description/
+
+Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
+
+Note:
+
+The solution set must not contain duplicate triplets.
+
+Example:
+
+Given array nums = [-1, 0, 1, 2, -1, -4],
+
+A solution set is:
+[
+  [-1, 0, 1],
+  [-1, -1, 2]
+]
+*/
+
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var threeSum = function(nums) {
+  var ret = [];
+  nums.sort(function(a, b) { return a - b });
+  for(var i = 0; i < nums.length; i++) {
+      if(i === 0 || i > 0 && nums[i] !== nums[i - 1]) {
+          var left = i + 1;
+          var right = nums.length - 1;
+          while(left < right) {
+              const sum = nums[left] + nums[right] + nums[i];
+              if(left > i + 1 && nums[left] === nums[left - 1] || sum < 0) {
+                  left++
+              } else if(right < nums.length - 1 && nums[right] === nums[right + 1] || sum > 0) {
+                  right--;
+              } else if(sum === 0) { 
+                  ret.push([nums[left], nums[right], nums[i]]);
+                  left++;
+                  right--;   
+              }
+          } 
+      }
+  }
+  
+  return ret;
+};
+
+var main = function() {
+  console.log(threeSum([]));
+  console.log(threeSum([-1, 0, 1, 2, -1, -4]));
+  console.log(threeSum([0]));
+  console.log(threeSum([0, 0]));
+  console.log(threeSum([0, 0, 0]));
+  console.log(threeSum([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]));
+}
+
+module.exports.main = main;

LeetcodeProblems/Min_Stack.js

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+/*
+Min Stack
+
+https://leetcode.com/problems/min-stack/description/
+
+Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
+
+push(x) -- Push element x onto stack.
+pop() -- Removes the element on top of the stack.
+top() -- Get the top element.
+getMin() -- Retrieve the minimum element in the stack.
+Example:
+MinStack minStack = new MinStack();
+minStack.push(-2);
+minStack.push(0);
+minStack.push(-3);
+minStack.getMin();   --> Returns -3.
+minStack.pop();
+minStack.top();      --> Returns 0.
+minStack.getMin();   --> Returns -2.
+*/
+
+class MinStack {
+  constructor() {
+    this.minStack = [];
+    this.stack = [];
+    this.countStack = 0;
+    this.countMinStack = 0;
+  }
+
+  push(value) {
+    if(this.countStack === this.stack.length)
+      this.stack.push(value);
+    else 
+      this.stack[this.countStack] = value;
+    this.countStack++;
+    
+    const min = this.getMin();
+    if(min === null || min >= value) {
+      if(this.countMinStack === this.minStack.length)
+        this.minStack.push(value);
+      else 
+        this.minStack[this.countMinStack] = value;
+      this.countMinStack++;
+    }
+  }
+
+  pop() {
+    if(this.countStack === 0)
+      return null;
+
+    var elem = this.stack[this.countStack - 1];
+    this.countStack--;
+    
+    if(elem === this.minStack[this.countMinStack - 1])
+      this.countMinStack--;
+
+    return elem;
+  }
+
+  top() {
+    if(this.countStack === 0)
+      return null;
+    
+    return this.stack[this.countStack - 1];
+  }
+
+  getMin() {
+    if(this.countMinStack === 0)
+      return null;
+
+    return this.minStack[this.countMinStack - 1]
+  }
+}
+
+var main = function() {
+  var minStack = new MinStack();
+  minStack.push(-2);
+  minStack.push(0);
+  minStack.push(-3);
+  console.log(minStack.getMin());
+  console.log(minStack.pop());
+  console.log(minStack.top());
+  console.log(minStack.getMin());
+}
+
+module.exports.main = main;

LeetcodeProblems/Sum_Of_Square_Numbers.js

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+/*
+Sum of Square Numbers
+https://leetcode.com/problems/sum-of-square-numbers/description/
+
+Given a non-negative integer c, your task is to decide whether there're two integers a and b such that a2 + b2 = c.
+
+Example 1:
+Input: 5
+Output: True
+Explanation: 1 * 1 + 2 * 2 = 5
+
+Example 2:
+Input: 3
+Output: False
+*/
+
+
+/**
+ * @param {number} c
+ * @return {boolean}
+ */
+var judgeSquareSum = function(c) {
+  var iter = 0;
+  var set = new Set();
+  while(iter ** 2 <= c) {
+    var square = iter * iter;
+    if(square * 2 === c || set.has(c - square))
+      return true;
+
+    set.add(square);
+    iter++;
+  }
+  
+  return false;
+};
+
+var main = function() {
+  console.log(judgeSquareSum(0));
+  console.log(judgeSquareSum(1));
+  console.log(judgeSquareSum(5));
+  console.log(judgeSquareSum(16));
+  console.log(judgeSquareSum(24));
+  console.log(judgeSquareSum(25));
+}