solution: longest increasing subsequence

Author: Jeongwon Na

longest-increasing-subsequence/njngwn.java

@@ -0,0 +1,23 @@
+// time complexity: O(nlogn), n: nums.length (logn because of binary search)
+// space complexity: O(n), n: nums.length
+class Solution {
+    public int lengthOfLIS(int[] nums) {
+        ArrayList<Integer> incSeqList = new ArrayList<Integer>();   // dp
+        incSeqList.add(nums[0]);
+
+        for (int num : nums) {
+            if (num > incSeqList.get(incSeqList.size()-1)) {
+                // add element to incSeqLit
+                incSeqList.add(num);
+            } else {
+                int idx = Collections.binarySearch(incSeqList, num);
+                if (idx < 0) {  // idx returns -(insertedPos + 1)
+                    int insertedIdx = -(idx + 1);
+                    incSeqList.set(insertedIdx, num);
+                }
+            }
+        }
+
+        return incSeqList.size();
+    }
+}