Update concepts

Author: Narahari-Sundaragopalan

concepts/HttpRequests-solutions.js renamed to concepts/HttpRequests-solutions.md

@@ -1,33 +1,21 @@
-/////////////////
-//             //
-// CHALLENGE 1 //
-//             //
-/////////////////
 
-// /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
-// console.log('Start of Challenge 1');
-// ...your code below
+### CHALLENGE 1
 
+```js
 console.log("I am at the beginning of the code");
 
 setTimeout(function() { console.log("I am in the setTimeout callback function after 3 seconds(3000ms)");}, 3000)
 
 console.log("I am at the end of the code");
 
 
-
 // console.log('End of Challenge 1');
 // */// (do not alter this line)
+```
 
+### CHALLENGE  2 
 
-
-
-/////////////////
-//             //
-// CHALLENGE 2 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 2');
 // ...your code below
@@ -49,15 +37,12 @@ function clearAllIntervals() {
 }
 console.log('End of Challenge 2');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 3
 
-/////////////////
-//             //
-// CHALLENGE 3 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 3');
 // ...your code below
@@ -82,16 +67,12 @@ function everyXSecsForYsecs(callback, xSecs, ySecs) {
 
 console.log('End of Challenge 3');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 4
 
-
-/////////////////
-//             //
-// CHALLENGE 4 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 4');
 // ...your code below
@@ -113,15 +94,12 @@ forEach(delays, delayLog);
 
 console.log('End of Challenge 4');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 5
 
-/////////////////
-//             //
-// CHALLENGE 5 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 5');
 // ...your code below
@@ -149,15 +127,12 @@ activateButton.addEventListener("click", function() {
 document.body.style.background = '#def';
 console.log('End of Challenge 3');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 6
 
-/////////////////
-//             //
-// CHALLENGE 6 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 6');
 var dataReceived;
@@ -186,15 +161,12 @@ console.log("Data is ", dataReceived);
 
 console.log('End of Challenge 6');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 7
 
-/////////////////
-//             //
-// CHALLENGE 7 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 7');
 // ...your code below
@@ -218,15 +190,12 @@ request.send();
 
 console.log('End of Challenge 7');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 8
 
-/////////////////
-//             //
-// CHALLENGE 8 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 8');
 // ...your code below
@@ -257,15 +226,12 @@ requestEvents.send();
 
 console.log('End of Challenge 8');
 // */// (do not alter this line)
+```
 
 
+### CHALLENGE 9
 
-/////////////////
-//             //
-// CHALLENGE 9 //
-//             //
-/////////////////
-
+```js
 // /* <<<=== Remove the first two slashes (//) to comment out this challenge when finished
 console.log('Start of Challenge 9');
 // ...your code below
@@ -293,11 +259,7 @@ requestEventsInUsa.open("GET", eventsAPIUSA);
 requestEventsInUsa.send();
 
 
-
-
-
-
 console.log('End of Challenge 9');
 // */// (do not alter this line)
-
+```
 

exercises/leetcode/amazon/numberOfIslands.js

@@ -32,7 +32,7 @@ const numberOfIslands = grid => {
 
     const isLand = (x, y) => {
         return x > -1 && x < grid.length && y > -1 &&
-                y < grid[0].length && grid[x, y] !== '0';
+                y < grid[0].length && grid[x][y] !== '0';
     }
 
     const removeIsland = (startX, startY) => {

exercises/leetcode/diameterOfBinaryTree.js

@@ -0,0 +1,26 @@
+class TreeNode {
+    constructor(val) {
+        this.val = val;
+        this.left = null;
+        this.right = null;
+    }
+}
+let ans;
+
+const maxDepth = node => {
+    if (!node) {
+        return 0;
+    }
+
+    let left = depth(node.left);
+    let right = depth(node.right);
+
+    ans = Math.max(ans, left + right + 1);
+
+    return Math.max(left, right) + 1;
+}
+const diameterOfBinaryTree = root => {
+    ans = 1;
+    maxDepth(root);
+    return ans - 1;
+}

exercises/leetcode/maxPathSumBinaryTree.js

@@ -0,0 +1,58 @@
+/**
+ * Given a non-empty binary tree, find the maximum path sum.
+
+For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path must contain at least one node and does not need to go through the root.
+
+Example 1:
+
+Input: [1,2,3]
+
+       1
+      / \
+     2   3
+
+Output: 6
+Example 2:
+
+Input: [-10,9,20,null,null,15,7]
+
+   -10
+   / \
+  9  20
+    /  \
+   15   7
+
+Output: 42
+ */
+
+class TreeNode {
+    constructor(val) {
+        this.val = val;
+        this.left = null;
+        this.right = null;
+    }
+}
+
+let maxSum;
+
+const maxGain = node => {
+    if (!node) {
+        return Number.NEGATIVE_INFINITY;
+    }
+
+    let leftGain = Math.max(maxGain(node.left), 0);
+    let rightGain = Math.max(maxGain(node.right), 0);
+
+    let newPathMax = node.val + leftGain + rightGain;
+
+    maxSum = Math.max(maxSum, newPathMax);
+
+    return node.val + Math.max(leftGain, rightGain);
+}
+const maxPathSum = root => {
+    maxSum = Number.NEGATIVE_INFINITY;
+
+    maxGain(root);
+
+    return maxSum;
+}