Competitive-Coding-2 complete

Problem1.java

@@ -0,0 +1,27 @@
+// 0-1 Knapsack problem
+// Time complexity: O(weights.length * capacity)
+// Space complexity: O(capacity) for dp array
+public class Problem1 {
+    public int maxProfit(int[] profits, int[] weights, int capacity) {
+        int[] dp = new int[capacity + 1];
+        for (int row = 1; row < weights.length + 1; row ++) {
+            // Iterating backwards to avoid using modified dp value.
+            for (int col = capacity; col >= 1; col --) {
+                if (col >= weights[row - 1]) { // col is the max capacity
+                    // Consider maximum between previous profit and sum of current weight's profit and maximum profit from the remaining weight.
+                    dp[col] = Math.max(dp[col], profits[row - 1] + (dp[col - weights[row - 1]]));
+                }
+            }
+        }
+        return dp[capacity];
+    }
+    public static void main(String[] args) {
+        Problem1 ob = new Problem1();
+        int[] profits = new int[] {1, 2, 3};
+        int[] weights = new int[] {4, 5, 1};
+        int capacity = 4;
+        System.out.println(ob.maxProfit(profits, weights, capacity));
+        capacity = 5;
+        System.out.println(ob.maxProfit(profits, weights, capacity));
+    }
+}

Problem2.java

@@ -0,0 +1,41 @@
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+// Approach: HashMap
+// Time: O(N)
+// Space: O(N) for HashMap
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> indexMap = new HashMap<>();
+        for (int i = 0; i < nums.length; i ++) {
+            if (indexMap.containsKey(target - nums[i])) {
+                return new int[] {indexMap.get(target - nums[i]), i};
+            }
+            indexMap.put(nums[i], i);
+        }
+        throw new IllegalArgumentException("No solution");
+    }
+
+    public static void main(String[] args) {
+        Solution ob = new Solution();
+
+        int[] nums1 = {2,7,11,15};
+        System.out.println(Arrays.toString(ob.twoSum(nums1, 9))); // returns [0, 1]
+
+        int[] nums2 = {3,2,4};
+        System.out.println(Arrays.toString(ob.twoSum(nums2, 6))); // returns [1, 2]
+
+        int[] nums3 = {3,3};
+        System.out.println(Arrays.toString(ob.twoSum(nums3, 6))); // returns [0, 1]
+
+        int[] nums4 = {3};
+        System.out.println(Arrays.toString(ob.twoSum(nums4, 3))); // throws exception
+
+        int[] nums5 = {};
+        System.out.println(Arrays.toString(ob.twoSum(nums5, 0))); // throws exception
+
+        int[] nums6 = {2, 3};
+        System.out.println(Arrays.toString(ob.twoSum(nums6, 4))); // throws exception
+    }
+}