Add LIS solution in TypeScript

Author: Jeehay28

longest-increasing-subsequence/Jeehay28.ts

@@ -0,0 +1,33 @@
+// Time Complexity: O(n * log n)
+// Space Complexity: O(n)
+
+function lengthOfLIS(nums: number[]): number {
+  const sub: number[] = []; // O(n)
+
+  for (const num of nums) { // O(n)
+    // lower bound binary search: find the first index where element >= target
+    let left = 0;
+    let right = sub.length;
+    const target = num;
+
+    while (left < right) { // O(log n)
+      let mid = Math.floor((left + right) / 2);
+      if (sub[mid] < target) {
+        left = mid + 1;
+      } else {
+        right = mid;
+      }
+    }
+
+    // if target is greater than all elements in sub
+    if (left === sub.length) {
+      sub.push(target);
+    } else {
+      // replace the first element >= target
+      sub[left] = target;
+    }
+  }
+
+  return sub.length;
+}
+