[hsskey] Week 08 Solutions

clone-graph/hsskey.js

@@ -0,0 +1,34 @@
+/**
+ * // Definition for a Node.
+ * function _Node(val, neighbors) {
+ *    this.val = val === undefined ? 0 : val;
+ *    this.neighbors = neighbors === undefined ? [] : neighbors;
+ * };
+ */
+
+/**
+ * @param {_Node} node
+ * @return {_Node}
+ */
+var cloneGraph = function(node) {
+    if (!node) return null;
+
+    const oldToNew = new Map();
+
+    const dfs = (node) => {
+        if (oldToNew.has(node)) {
+            return oldToNew.get(node);
+        }
+
+        const copy = new _Node(node.val);
+        oldToNew.set(node, copy);
+
+        for (let neighbor of node.neighbors) {
+            copy.neighbors.push(dfs(neighbor));
+        }
+
+        return copy;
+    };
+
+    return dfs(node);
+};

longest-common-subsequence/hsskey.js

@@ -0,0 +1,23 @@
+/**
+ * @param {string} text1
+ * @param {string} text2
+ * @return {number}
+ */
+var longestCommonSubsequence = function(text1, text2) {
+    const m = text1.length;
+    const n = text2.length;
+
+    const dp = Array.from({ length: m + 1 }, () => Array(n + 1).fill(0));
+
+    for (let i = m - 1; i >= 0; i--) {
+        for (let j = n - 1; j >= 0; j--) {
+            if (text1[i] === text2[j]) {
+                dp[i][j] = 1 + dp[i + 1][j + 1];
+            } else {
+                dp[i][j] = Math.max(dp[i + 1][j], dp[i][j + 1]);
+            }
+        }
+    }
+
+    return dp[0][0];
+};

longest-repeating-character-replacement/hsskey.js

@@ -0,0 +1,25 @@
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var characterReplacement = function(s, k) {
+    const count = {};
+    let res = 0;
+    let l = 0;
+    let maxf = 0;
+
+    for (let r = 0; r < s.length; r++) {
+        count[s[r]] = (count[s[r]] || 0) + 1;
+        maxf = Math.max(maxf, count[s[r]]);
+
+        while ((r - l + 1) - maxf > k) {
+            count[s[l]] -= 1;
+            l += 1;
+        }
+
+        res = Math.max(res, r - l + 1);
+    }
+
+    return res;
+};

palindromic-substrings/hsskey.js

@@ -0,0 +1,24 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var countSubstrings = function(s) {
+    let res = 0;
+
+    const countPali = (s, l, r) => {
+        let count = 0;
+        while (l >= 0 && r < s.length && s[l] === s[r]) {
+            count++;
+            l--;
+            r++;
+        }
+        return count;
+    };
+
+    for (let i = 0; i < s.length; i++) {
+        res += countPali(s, i, i);
+        res += countPali(s, i, i + 1);
+    }
+
+    return res;
+};

reverse-bits/hsskey.js

@@ -0,0 +1,12 @@
+/**
+ * @param {number} n - a positive integer
+ * @return {number} - a positive integer
+ */
+var reverseBits = function(n) {
+    let res = 0;
+    for (let i = 0; i < 32; i++) {
+        let bit = (n >>> i) & 1;
+        res |= (bit << (31 - i));
+    }
+    return res >>> 0;
+};