[Moonjonghoo] WEEK 02 solutions

3sum/moonjonghoo.js

@@ -0,0 +1,36 @@
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+
+var threeSum = function (nums) {
+  let result = [];
+  nums.sort((a, b) => a - b);
+
+  for (let i = 0; i < nums.length - 2; i++) {
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+
+    let left = i + 1;
+    let right = nums.length - 1;
+
+    while (left < right) {
+      const sum = nums[i] + nums[left] + nums[right];
+
+      if (sum === 0) {
+        result.push([nums[i], nums[left], nums[right]]);
+
+        while (left < right && nums[left] === nums[left + 1]) left++;
+        while (left < right && nums[right] === nums[right - 1]) right--;
+
+        left++;
+        right--;
+      } else if (sum < 0) {
+        left++;
+      } else {
+        right--;
+      }
+    }
+  }
+
+  return result;
+};

climbing-stairs/moonjonghoo.js

@@ -0,0 +1,16 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function (n) {
+  let dp = new Array(n + 1);
+  dp[1] = 1;
+  dp[2] = 2;
+  for (let i = 3; i <= n; i++) {
+    dp[i] = dp[i - 1] + dp[i - 2];
+  }
+  return dp[n];
+};
+
+console.log(climbStairs(2));
+console.log(climbStairs(3));

product-of-array-except-self/moonjonghoo.js

@@ -0,0 +1,22 @@
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var productExceptSelf = function (nums) {
+  let answer = [];
+  answer[0] = 1;
+
+  for (let i = 1; i < nums.length; i++) {
+    answer[i] = answer[i - 1] * nums[i - 1];
+  }
+  let right = 1;
+
+  for (let i = nums.length - 1; i >= 0; i--) {
+    answer[i] *= right;
+    right *= nums[i];
+  }
+  return answer;
+};
+
+productExceptSelf([1, 2, 3, 4]);
+productExceptSelf([-1, 1, 0, -3, 3]);

valid-anagram/moonjonghoo.js

@@ -0,0 +1,29 @@
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {boolean}
+ */
+var isAnagram = function (s, t) {
+  if (s.length !== t.length) return false;
+  let hashMap = new Map();
+  for (let i = 0; i < s.length; i++) {
+    if (hashMap.has(s[i])) {
+      hashMap.set(s[i], hashMap.get(s[i]) + 1);
+    } else {
+      hashMap.set(s[i], 1);
+    }
+  }
+  for (let i = 0; i < t.length; i++) {
+    if (hashMap.has(t[i])) {
+      hashMap.set(t[i], hashMap.get(t[i]) - 1);
+      if (hashMap.get(t[i]) === 0) {
+        hashMap.delete(t[i]);
+      }
+    }
+  }
+
+  if (hashMap.size === 0) return true;
+  else return false;
+};
+
+isAnagram("anagram", "nagaram");