[soobing] WEEK 04 Solutions

coin-change/soobing3.ts

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+function coinChange(coins: number[], amount: number): number {
+  const dp = new Array(amount + 1).fill(Infinity);
+  dp[0] = 0;
+
+  for (let i = 0; i <= amount; i++) {
+      for(const coin of coins) {
+          if (i - coin >= 0 && dp[i - coin] !== Infinity) {
+              dp[i] = Math.min(dp[i], dp[i - coin] + 1);
+          }
+      }
+  }
+  return dp[amount] === Infinity ? -1 : dp[amount];
+};
+

find-minimum-in-rotated-sorted-array/soobing3.ts

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+function findMin(nums: number[]): number {
+  let left = 0;
+  let right = nums.length - 1;
+  while(left < right) {
+      const mid = Math.floor((left + right) / 2);
+      if(nums[mid] > nums[right]) {
+          left = mid + 1;
+      } else {
+          right = mid;
+      }
+  }
+  return nums[left];
+};

maximum-depth-of-binary-tree/soobing3.ts

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+
+class TreeNode {
+    val: number
+    left: TreeNode | null
+    right: TreeNode | null
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = (val===undefined ? 0 : val)
+        this.left = (left===undefined ? null : left)
+        this.right = (right===undefined ? null : right)
+    }
+}
+
+function maxDepth(root: TreeNode | null): number {
+  if(!root) return 0;
+  return 1 + Math.max(maxDepth(root.left), maxDepth(root.right))
+};

merge-two-sorted-lists/soobing3.ts

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+
+class ListNode {
+    val: number
+    next: ListNode | null
+    constructor(val?: number, next?: ListNode | null) {
+        this.val = (val===undefined ? 0 : val)
+        this.next = (next===undefined ? null : next)
+    }
+}
+
+
+function mergeTwoLists(list1: ListNode | null, list2: ListNode | null): ListNode | null {
+  let mergedList = new ListNode(0, null);
+  const result = mergedList;
+
+  while(list1 && list2) {
+      if(list1.val < list2.val) {
+          mergedList.next = list1;
+          list1 = list1.next;
+      } else {
+          mergedList.next = list2;
+          list2 = list2.next;
+      }
+      mergedList = mergedList.next;
+  }
+
+  mergedList.next = list1 ?? list2;
+
+  return result.next;
+};

word-search/soobing3.ts

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+function exist(board: string[][], word: string): boolean {
+  const move = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+  function dfs(row: number, col: number, index: number) {
+      if(board[row][col] !== word[index]) return false;
+
+      const temp = board[row][col];
+      board[row][col] = '#';
+
+      if(index === word.length - 1) return true;
+      for(const [dx, dy] of move) {
+          if(row + dx < 0 || row + dx >= board.length) continue;
+          if(col + dy < 0 || col + dy >= board[0].length) continue;
+          if(dfs(row + dx, col + dy, index + 1)) return true;
+      }
+
+      board[row][col] = temp;
+  }
+
+  for (let r = 0; r < board.length; r++) {
+    for (let c = 0; c < board[0].length; c++) {
+        if (dfs(r, c, 0)) return true;
+    }
+}
+  return false;
+};