[pepper] Week 6 Solutions

container-with-most-water/whewchews.ts

@@ -0,0 +1,24 @@
+function maxArea(height: number[]): number {
+  let left = 0;
+  let right = height.length - 1;
+  let maxSize = 0;
+
+  while (left < right) {
+    maxSize = Math.max(maxSize, getMaxSize(height, left, right));
+
+    if (height[left] < height[right]) {
+      left++;
+    } else {
+      right--;
+    }
+  }
+
+  return maxSize;
+}
+
+function getMaxSize(height: number[], left: number, right: number) {
+  return Math.min(...[height[right], height[left]]) * (right - left);
+}
+
+// TC: O(n)
+// SC: O(1)

design-add-and-search-words-data-structure/whewchews.ts

@@ -0,0 +1,48 @@
+class WordDictionary {
+  wordList: Set<string>;
+  wordCountMap: Map<number, string[]>;
+  constructor() {
+    this.wordList = new Set();
+    this.wordCountMap = new Map();
+  }
+
+  // TC: O(1)
+  // SC: O(n)
+  addWord(word: string): void {
+    this.wordList.add(word);
+    const length = word.length;
+    if (this.wordCountMap.has(length)) {
+      this.wordCountMap.get(length).push(word);
+    } else {
+      this.wordCountMap.set(length, [word]);
+    }
+    return null;
+  }
+
+  // TC: O(m*n) // m: words length, n: word length
+  // SC: O(1)
+  search(word: string): boolean {
+    const len = word.length;
+    const targetWord = word.replace(/\./g, "");
+    const hasDot = len - targetWord.length !== 0;
+
+    if (!hasDot) return this.wordList.has(word);
+    if (!this.wordCountMap.has(len)) {
+      return false;
+    }
+    const words = this.wordCountMap.get(len);
+    for (let i = 0; i < words.length; i++) {
+      let match = true;
+      for (let j = 0; j < words[i].length; j++) {
+        if (word[j] !== "." && word[j] !== words[i][j]) {
+          match = false;
+          break;
+        }
+      }
+      if (match) {
+        return true;
+      }
+    }
+    return false;
+  }
+}

spiral-matrix/whewchews.ts

@@ -0,0 +1,39 @@
+function spiralOrder(matrix: number[][]): number[] {
+  const rows = matrix.length;
+  const cols = matrix[0].length;
+  const total = rows * cols;
+  let srow = 0; // start row
+  let scol = 0;
+  let erow = rows - 1; // end row
+  let ecol = cols - 1;
+  let count = 0;
+  const ans: number[] = [];
+
+  while (count < total) {
+    for (let i = scol; i <= ecol && count < total; i++) {
+      ans.push(matrix[srow][i]);
+      count++;
+    }
+    srow++;
+    for (let i = srow; i <= erow && count < total; i++) {
+      ans.push(matrix[i][ecol]);
+      count++;
+    }
+    ecol--;
+    for (let i = ecol; i >= scol && count < total; i--) {
+      ans.push(matrix[erow][i]);
+      count++;
+    }
+    erow--;
+    for (let i = erow; i >= srow && count < total; i--) {
+      ans.push(matrix[i][scol]);
+      count++;
+    }
+    scol++;
+  }
+
+  return ans;
+}
+
+// TC: O(m*n)
+// SC: O(m*n)

valid-parentheses/whewchews.ts

@@ -0,0 +1,38 @@
+/*
+ * 아이디어
+ * stack 자료구조를 사용해 여는 괄호가 나오면 순서대로 저장해둔다.
+ * stack을 사용하는 이유는 가장 최근 여는 괄호가 어떤 것인지 확인하기 위함이다.(마지막에 삽입한 값을 먼저 사용함)
+ * 닫는 괄호가 나오면 stack의 마지막 값이 pair인 여는 괄호인지 체크한다. 다르면 return false
+ * 문자열 반복문을 다 돌고 stack에 여는 괄호가 남아있지 않은지 본다. 남아있으면 return false
+ * 위의 두 경우에 해당되지 않으면 return true
+ */
+function isValid(s: string): boolean {
+  const charSet = new Set(["(", "{", "["]);
+  const openCharStack = [];
+  const CHAR_PAIR = {
+    "]": "[",
+    "}": "{",
+    ")": "(",
+  };
+
+  for (let i = 0; i <= s.length - 1; i++) {
+    const char = s[i];
+    if (charSet.has(char)) {
+      openCharStack.push(char);
+      continue;
+    }
+
+    if (char in CHAR_PAIR) {
+      const pair = CHAR_PAIR[char];
+      const lastOpenChar = openCharStack.pop();
+      if (lastOpenChar !== pair) {
+        return false;
+      }
+    }
+  }
+
+  const isEmpty = openCharStack.length === 0;
+  return isEmpty;
+}
+// TC: O(n)
+// SC: O(n)