- Add: Java solutions

Author: BNSC1

LeetCode/155. Min Stack.java

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+class MinStack {
+    LinkedList<Node> st = new LinkedList<>();
+
+    public MinStack() {} //SC: O(count of elements)
+    
+    public void push(int val) {
+        if (!st.isEmpty()) {
+            st.push(new Node(val, st.peek().minVal));
+        } else {
+            st.push(new Node(val, Integer.MAX_VALUE));
+        }
+    } //TC: O(1)
+    
+    public void pop() {
+        st.poll();
+    } //TC: O(1)
+    
+    public int top() {
+        return st.peek().val;
+    } //TC: O(1)
+    
+    public int getMin() {
+        return st.peek().minVal;
+    } //TC: O(1)
+}
+class Node {
+    int minVal = Integer.MAX_VALUE;
+    int val = 0;
+    Node(int val, int lastMin) {
+        this.val = val;
+        this.minVal = Math.min(lastMin, this.val);
+    }
+}
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * MinStack obj = new MinStack();
+ * obj.push(val);
+ * obj.pop();
+ * int param_3 = obj.top();
+ * int param_4 = obj.getMin();
+ */

Pramp/Flatten a Dictionary.java

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+import java.io.*;
+import java.util.*;
+
+class Solution {
+
+  static HashMap<String, String> flattenDictionary(HashMap<String, Object> dict) {
+      HashMap<String, String> res = new HashMap<>();
+      class Helper {
+          void dfs(String prefix, Object o) {
+              if (o instanceof Map) {
+                  for (Map.Entry<String, Object> e : ((Map<String, Object>) o).entrySet()) {
+                    String newPrefix = prefix;
+                    if (e.getKey() != "" && prefix != "") {
+                      newPrefix += ".";
+                    }
+                    dfs(newPrefix + e.getKey(), e.getValue());
+                  }
+              } else {
+                  res.put(prefix, (String)o);
+              }
+          }
+      }
+      Helper h = new Helper();
+      for (Map.Entry<String, Object> e : dict.entrySet()) {
+          h.dfs(e.getKey(), e.getValue());
+      }
+
+      return res;
+  }
+
+    public static void main(String[] args) {
+
+    }
+
+}