twoSum and graphValidTree solutions

dipti95 · dipti95 · commit 7f59c0ef26a5 · 2022-07-06T20:04:27.000-04:00
diff --git a/typescript/1-Two-Sum.ts b/typescript/1-Two-Sum.ts
@@ -0,0 +1,11 @@
+function twoSum(nums: number[], target: number): number[] {
+  let hash: { [key: number]: number } = {}
+  for (let i = 0; i < nums.length; i++) {
+    let diff = target - nums[i]
+    if (diff in hash) {
+      return [hash[diff], i]
+    } else {
+      hash[nums[i]] = i
+    }
+  }
+}
diff --git a/typescript/261-Graph-Valid-Tree.ts b/typescript/261-Graph-Valid-Tree.ts
@@ -0,0 +1,42 @@
+interface Obj {
+  [key: number]: Array<number>
+}
+
+interface Visited {
+  [key: number]: boolean
+}
+
+function validTree(n: number, edges: number[][]): boolean {
+  if (n === 0) return true
+
+  let adjacent: Obj = {}
+  let visited: Visited = {}
+  for (let i = 0; i < n; i++) {
+    adjacent[i] = []
+  }
+
+  for (const val of edges) {
+    const [n1, n2] = val
+    adjacent[n1].push(n2)
+    adjacent[n2].push(n1)
+  }
+
+  return dfs(0, -1, visited, adjacent) && Object.keys(visited).length === n
+}
+
+function dfs(
+  node: number,
+  prevNode: number,
+  visited: Visited,
+  adjacent: Obj
+): boolean {
+  if (visited[node]) return false
+  visited[node] = true
+
+  for (const ele of adjacent[node]) {
+    if (ele === prevNode) continue
+    if (!dfs(ele, node, visited, adjacent)) return false
+  }
+
+  return true
+}
