[tedkimdev] WEEK 9 Solutions

linked-list-cycle/tedkimdev.go

@@ -0,0 +1,23 @@
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+
+// TC: O(n)
+// SC: O(1)
+func hasCycle(head *ListNode) bool {
+	slow := head
+	fast := head
+	for fast != nil && fast.Next != nil {
+		slow = slow.Next
+		fast = fast.Next.Next
+		if slow == fast {
+			return true
+		}
+	}
+
+	return false
+}

minimum-window-substring/tedkimdev.go

@@ -0,0 +1,55 @@
+// TC: O(n * m)
+// SC: O(n + m)
+
+func minWindow(s string, t string) string {
+	if len(t) > len(s) {
+		return ""
+	}
+
+	countT := map[byte]int{}
+	for i := 0; i < len(t); i++ {
+		countT[t[i]]++
+	}
+
+	windowMap := map[byte]int{}
+	have, need := 0, len(countT)
+
+	left := 0
+	resLeft, resRight := -1, -1
+	resLen := len(s) + 1
+
+	for right := 0; right < len(s); right++ {
+		c := s[right]
+		windowMap[c]++
+
+		// update have
+		if count, ok := countT[c]; ok {
+			if windowMap[c] == count {
+				have++
+			}
+		}
+
+		// window valid -> move left to find minimum
+		for have == need {
+			if right-left+1 < resLen {
+				resLen = right - left + 1
+				resLeft, resRight = left, right
+			}
+
+			// remove left char
+			lc := s[left]
+			if count, ok := countT[lc]; ok {
+				if windowMap[lc] == count {
+					have--
+				}
+			}
+			windowMap[lc]--
+			left++
+		}
+	}
+
+	if resLeft == -1 {
+		return ""
+	}
+	return s[resLeft : resRight+1]
+}