add: 증가하는 최대 부분수열

Author: Yongseok-Choi-dev

longest-increasing-subsequence/YoungSeok-Choi.java

@@ -0,0 +1,69 @@
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+// tc: O(n)
+// idea: max largest subseq length for "N" th array index
+class Solution {
+
+    public int lengthOfLIS(int[] nums) {
+
+        int[] arr = new int[nums.length];
+        Arrays.fill(arr, 1);
+
+        for(int i = 1; i < nums.length; i++) {
+            for(int j = 0; j < i; j++) {
+                if(nums[j] < nums[i]) {
+                    arr[i] = Math.max(arr[i], arr[j] + 1);
+                }
+            }
+        }
+
+        int mx = -987654321;
+        for(int anInt : arr) {
+            System.out.print(anInt + " ");
+            mx = Math.max(mx, anInt);
+        }
+        
+        return mx;
+    }
+}
+
+// time limit exceed
+
+class WrongSolution {
+
+    public boolean[] visit;
+    public int mxVal = -987654321;
+    public int mx = 1;
+    public Map<Integer, Boolean> m = new HashMap<>();
+
+    public int lengthOfLIS(int[] nums) {
+        for(int i = 0; i < nums.length; i++) {
+            m = new HashMap<>();
+            mxVal = Math.max(mxVal, nums[i]);
+            m.put(nums[i], true);
+            dfs(i, nums);
+            mxVal = -987654321;
+        }
+
+        return mx;   
+    }
+
+    public void dfs(int idx, int[] nums) {
+        mx = Math.max(mx, m.size());
+
+        for(int i = idx + 1; i < nums.length; i++) {
+            if(mxVal < nums[i]) {
+                int prev = mxVal;
+                mxVal = nums[i];
+                m.put(nums[i], true);
+
+                dfs(i, nums);
+
+                mxVal = prev;
+                m.remove(nums[i]);
+            }            
+        }
+    }
+}