All code moved and renamed.

Author: omprashantjain

14 Hashing and Maps/TwoSum.java …ms/Leetcode 1 Two Sum using Hashmap.java14 Hashing and Maps/TwoSum.java renamed to 1 Leetcode Easy Problems/Leetcode 1 Two Sum using Hashmap.java 14 Hashing and Maps/TwoSum.java renamed to 1 Leetcode Easy Problems/Leetcode 1 Two Sum using Hashmap.java

@@ -0,0 +1,30 @@
+import java.util.*;
+
+class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> result = new ArrayList<>();
+        for (int i = 0; i < numRows; i++) {
+            List<Integer> genRow = generateRow(i+1);
+            result.add(genRow);
+        }
+        return result;
+    }
+
+    private List<Integer> generateRow(int rowNumber) {
+        if (rowNumber == 1) {
+            List<Integer> firstRow = new ArrayList<>();
+            firstRow.add(1);
+            return firstRow;
+        }
+
+        List<Integer> currRow = new ArrayList<>();
+        List<Integer> prevRow = generateRow(rowNumber - 1);
+
+        currRow.add(1);
+        for (int i = 1; i < rowNumber - 1; i++) {
+            currRow.add(prevRow.get(i-1) + prevRow.get(i));
+        }
+        currRow.add(1);
+        return currRow;
+    }
+}

17 DFS and BFS/PathSum.java …Easy Problems/Leetcode 112 Path Sum.java17 DFS and BFS/PathSum.java renamed to 1 Leetcode Easy Problems/Leetcode 112 Path Sum.java 17 DFS and BFS/PathSum.java renamed to 1 Leetcode Easy Problems/Leetcode 112 Path Sum.java

@@ -0,0 +1,19 @@
+class Solution {
+    public int maxProfit(int[] prices) {
+        int maxProfit = 0;
+        int minPrice = Integer.MAX_VALUE;
+
+        for (int i = 0; i < prices.length; i++) {
+            if (minPrice > prices[i]) {
+                minPrice = prices[i];
+            } else {
+                int profit = prices[i] - minPrice;
+                if (profit > maxProfit) {
+                    maxProfit = profit;
+                }
+            }
+        }
+
+        return maxProfit;
+    }
+}

1 Leetcode Easy Problems/Leetcode 118 Pascal's Triangle using Recursion.java

@@ -1,19 +1,14 @@
 class Solution {
-  public int maxProfit(int[] prices) {
-      int maxProfit = 0;
-      int minPrice = Integer.MAX_VALUE;
-
-      for (int i = 0; i < prices.length; i++) {
-          if (minPrice > prices[i]) {
-              minPrice = prices[i];
-          } else {
-              int profit = prices[i] - minPrice;
-              if (profit > maxProfit) {
-                  maxProfit = profit;
-              }
-          }
-      }
-
-      return maxProfit;
-  }
+    public int maxProfit(int[] prices) {
+        int maxProfit = 0;
+        for (int i = 0; i < prices.length - 1; i++) {
+            for (int j = i + 1; j < prices.length; j++) {
+                int profit = prices[j] - prices[i];
+                if (profit > maxProfit) {
+                    maxProfit = profit;
+                }
+            }
+        }
+        return maxProfit;
+    }
 }

…18 Pascals Triangle using Recursion.java … Triangle using Dynamic Programming.java1 Leetcode Easy Problems/Leetcode 118 Pascals Triangle using Recursion.java renamed to 1 Leetcode Easy Problems/Leetcode 118 Pascals Triangle using Dynamic Programming.java 1 Leetcode Easy Problems/Leetcode 118 Pascals Triangle using Recursion.java renamed to 1 Leetcode Easy Problems/Leetcode 118 Pascals Triangle using Dynamic Programming.java

@@ -0,0 +1,42 @@
+class Solution {
+  private final String[][] SYMBOLS = new String[][]{
+      {"I", "1"},
+      {"V", "5"},
+      {"X", "10"},
+      {"L", "50"},
+      {"C", "100"},
+      {"D", "500"},
+      {"M", "1000"},
+  };
+
+  private int getSymbolValue(char symbol) {
+      for (String[] row: SYMBOLS) {
+          if (row[0].equals(symbol + "")) {
+              return Integer.parseInt(row[1]);
+          }
+      }
+      return 0;
+  }
+
+  public int romanToInt(String s) {
+      int result = 0;
+      for (int i = 0; i < s.length(); i++) {
+          char current = s.charAt(i);
+          int currValue = getSymbolValue(current);
+
+          if (i + 1 < s.length()) {
+              char next = s.charAt(i+1);
+              int nextVal = getSymbolValue(next);
+              if (nextVal <= currValue) {
+                  result += currValue;
+              } else {
+                  result += (nextVal - currValue);
+                  i++;
+              }
+          } else {
+              result += currValue;
+          }
+      }
+      return result;
+  }
+}

1 Leetcode Easy Problems/Leetcode 121 Best Time to Buy and Sell Stock using Greedy.java

@@ -0,0 +1,28 @@
+import java.util.*;
+
+class Solution {
+    public int majorityElement(int[] nums) {
+        Map<Integer, Integer> cardi = getCardinalityMap(nums);
+        // Space: O(1), Time: O(n)
+        for (Map.Entry<Integer, Integer> entry : cardi.entrySet()) {
+            if (entry.getValue() > nums.length / 2) {
+                return entry.getKey();
+            }
+        }
+        return -1;
+    }
+
+    // Space: O(n), Time: O(n)
+    private Map<Integer, Integer> getCardinalityMap(int[] nums) {
+        Map<Integer, Integer> cardi = new HashMap<>();
+        for (int num: nums) {
+            if (!cardi.containsKey(num)) {
+                cardi.put(num, 1);
+            } else {
+                int currCount = cardi.get(num);
+                cardi.put(num, currCount + 1);
+            }
+        }
+        return cardi;
+    }
+}