[robinyoon-dev] WEEK 05 Solutions

best-time-to-buy-and-sell-stock/robinyoon-dev.js

@@ -23,7 +23,6 @@ var maxProfit = function (prices) {
     return maxProfit;
 };
 
-
 // -----아래는 이전에 작성한 답안입니다.
 // /**
 //  * @param {number[]} prices

group-anagrams/robinyoon-dev.js

@@ -0,0 +1,45 @@
+/**
+ * @param {string[]} strs
+ * @return {string[][]}
+ */
+
+// 문제는 풀었으나 시간 복잡도 측면에서 효율이 너무 떨어지는 풀이 방법....
+var groupAnagrams = function (strs) {
+    let outputArr = [];
+    let countArr = [];
+
+    const A_ASCII = 'a'.charCodeAt(0);
+    const Z_ASCII = 'z'.charCodeAt(0);
+
+    let charCounts = Z_ASCII - A_ASCII + 1;
+    let charCountArr = new Array(charCounts).fill(0); //인덱스가 알파벳을 나타냄.
+
+    for (str of strs) {
+        let strCountString = getStrCountString(str);
+
+        let hasSameCountIndex = countArr.findIndex((item) => item === strCountString);
+
+        if (hasSameCountIndex !== -1) {
+            outputArr[hasSameCountIndex].push(str);
+        } else {
+            countArr.push(strCountString);
+
+            outputArr.push([str]);
+        }
+    }
+
+    return outputArr;
+
+    function getStrCountString(str) {
+        let tempArr = [...charCountArr];
+
+        for (char of str) {
+            let charAscii = char.charCodeAt(0);
+            let charIndex = charAscii - A_ASCII;
+            tempArr[charIndex] += 1;
+        }
+        return tempArr.join(',');
+    }
+};
+
+

implement-trie-prefix-tree/robinyoon-dev.js

@@ -0,0 +1,68 @@
+// 문제풀이 해설 보고 푼 문제입니다.
+
+var TrieNode = function () {
+    this.children = {};
+    this.isEnd = false;
+}
+
+var Trie = function () {
+    this.root = new TrieNode();
+};
+
+/** 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function (word) {
+    let currentNode = this.root;
+    for (let i = 0; i < word.length; i++) {
+        let char = word[i];
+        if (!currentNode.children[char]) {
+            currentNode.children[char] = new TrieNode();
+
+        }
+        currentNode = currentNode.children[char];
+    }
+
+    currentNode.isEnd = true;
+};
+
+/** 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function (word) {
+    let currentNode = this.root;
+    for (let i = 0; i < word.length; i++) {
+        let char = word[i];
+        if (!currentNode.children[char]) {
+            return false;
+        }
+        currentNode = currentNode.children[char];
+    }
+    return currentNode.isEnd;
+};
+
+/** 
+ * @param {string} prefix
+ * @return {boolean}
+ */
+Trie.prototype.startsWith = function (prefix) {
+    let currentNode = this.root;
+    for (let i = 0; i < prefix.length; i++) {
+        let char = prefix[i];
+        if (!currentNode.children[char]) {
+            return false;
+        }
+        currentNode = currentNode.children[char];
+    }
+    return true;
+};
+
+/** 
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */

word-break/robinyoon-dev.js

@@ -0,0 +1,27 @@
+// 문풀 해설 보고 푼 문제
+/**
+ * @param {string} s
+ * @param {string[]} wordDict
+ * @return {boolean}
+ */
+var wordBreak = function (s, wordDict) {
+
+    const dp = new Array(s.length + 1).fill(false);
+    dp[0] = true;
+
+    let maxLength = 0;
+    for (let word of wordDict) {
+        maxLength = Math.max(maxLength, word.length);
+    }
+
+    for (let i = 1; i <= s.length; i++) {
+        for (let j = Math.max(0, i - maxLength); j < i; j++) {
+            if (dp[j] && wordDict.includes(s.substring(j, i))) {
+                dp[i] = true;
+                break;
+            }
+        }
+    }
+
+    return dp[s.length];
+};