Design Browser History (#1472, java, py) + Add and Search Words Data Structure (#211, py)

* 1472. Design Browser History
* problem 211: Design Add and Search Words Data Structure

Author: sumanth-botlagunta

Diff for: python/design_add_and_search_words_data_structure.py

@@ -0,0 +1,36 @@
+class Trienode:
+    def __init__(self):
+        self.children = {}
+        self.word = False
+
+class WordDictionary:
+
+    def __init__(self):
+        self.root = Trienode()
+        
+
+    def addWord(self, word: str) -> None:
+        ptr = self.root
+        for ch in word:
+            if ch not in ptr.children:
+                ptr.children[ch] = Trienode()
+            ptr = ptr.children[ch]
+        ptr.word = True
+        
+
+    def search(self, word: str) -> bool:
+        def dfs(j, root):
+            curr = root
+            for i in range(j, len(word)):
+                ch = word[i]
+                if ch == ".":
+                    for child in curr.children.values():
+                        if dfs(i+1, child):
+                            return True
+                    return False
+                else:
+                    if ch not in curr.children:
+                        return False
+                    curr = curr.children[ch]
+            return curr.word
+        return dfs(0, self.root)

Diff for: python/design_browser_history.py

@@ -0,0 +1,18 @@
+class BrowserHistory:
+
+    def __init__(self, homepage: str):
+        self.history = [homepage]
+        self.ptr = 0 
+
+    def visit(self, url: str) -> None:
+        self.ptr += 1
+        self.history = self.history[:self.ptr]
+        self.history.append(url)
+               
+    def back(self, steps: int) -> str:
+        self.ptr = max(0, self.ptr - steps)
+        return self.history[self.ptr]
+
+    def forward(self, steps: int) -> str:
+        self.ptr = min(len(self.history) - 1, self.ptr + steps)
+        return self.history[self.ptr]    

Diff for: src/DesignBrowserHistory.java

@@ -0,0 +1,26 @@
+class BrowserHistory {
+    private List<String> history;
+    private int ptr;
+
+    public BrowserHistory(String homepage) {
+        this.history = new ArrayList<>();
+        this.history.add(homepage);
+        this.ptr = 0;
+    }
+
+    public void visit(String url) {
+        this.ptr++;
+        this.history = this.history.subList(0, this.ptr);
+        this.history.add(url);
+    }
+
+    public String back(int steps) {
+        this.ptr = Math.max(0, this.ptr - steps);
+        return this.history.get(this.ptr);
+    }
+
+    public String forward(int steps) {
+        this.ptr = Math.min(this.history.size() - 1, this.ptr + steps);
+        return this.history.get(this.ptr);
+    }
+}