Create 300. Longest Increasing Subsequence

Author: khushi3004

300. Longest Increasing Subsequence

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+//Recursion - Brute force (TLE)
+
+class Solution {
+    public int lengthOfLIS(int[] nums) {
+        if(nums.length <= 1) return nums.length;
+         return lis(nums, 0, -1);
+    }
+
+    private int lis(int[] nums, int currentInd, int prevInd) {
+
+        if(currentInd == nums.length) return 0;
+        int skip = lis(nums, currentInd + 1, prevInd);
+        int select = -1;
+        if(prevInd == -1 || nums[currentInd] > nums[prevInd]) {
+            select = 1 + lis(nums, currentInd+1, currentInd);
+        }
+
+        return Math.max(skip, select);
+    }
+
+}
+
+//Recursion + Memoization
+
+class Solution {
+    public int lengthOfLIS(int[] nums) {
+        int n = nums.length;
+        if(n <= 1) return n;
+
+        int[][] dp = new int[n][n+1];
+
+        for(int[] rows : dp) {
+            Arrays.fill(rows, -1);
+        }
+
+         return lis(nums, 0, -1, dp);
+    }
+
+    private int lis(int[] nums, int currentInd, int prevInd, int[][] dp) {
+
+        if(currentInd == nums.length) return 0;
+
+        if(dp[currentInd][prevInd+1] != -1) return dp[currentInd][prevInd+1];
+
+        int skip = lis(nums, currentInd + 1, prevInd, dp);
+        int select = -1;
+        if(prevInd == -1 || nums[currentInd] > nums[prevInd]) {
+            select = 1 + lis(nums, currentInd+1, currentInd, dp);
+        }
+
+        dp[currentInd][prevInd+1] = Math.max(skip, select);
+
+        return dp[currentInd][prevInd+1];
+    }
+
+}
+
+//DP
+
+class Solution {
+    public int lengthOfLIS(int[] nums) {
+        int n = nums.length;
+        if(n <= 1) return n;
+
+        int[] dp = new int[n];
+
+        Arrays.fill(dp, 1);
+
+        int maxLength = 0;
+
+        for(int i = 1; i < n; i++) {
+            for(int j = 0; j < i; j++) {
+                if(nums[i] > nums[j]) {
+                    dp[i] = Math.max(dp[i], 1+dp[j]);
+                }
+            }
+            maxLength = Math.max(maxLength, dp[i]);
+        }
+
+        return maxLength;
+    }
+
+}