Added one solution & modified 2 solutions

varunu28 · varunu28 · commit ee9d31ebb83f · 2020-02-06T07:26:08.000-08:00
diff --git a/Easy/Day of the Week.java b/Easy/Day of the Week.java
@@ -0,0 +1,30 @@
+class Solution {
+    int[] m = {0,31,28,31,30,31,30,31,31,30,31,30,31};
+    String[] res = {"Friday", "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday"};
+    public String dayOfTheWeek(int day, int month, int year) {
+      int days = years(year);
+      if(isLeap(year))
+        m[2] = 29;
+      for(int i=0; i < month; i++){
+        days += m[i];
+      }
+      days += day-1;
+      return res[days%7];
+    }
+    private int years(int y){
+      int count = 0;
+      for(int i=1971; i < y; i++){
+        if(isLeap(i))
+         count += 366;    
+        else
+         count += 365;    
+      }
+      return count;
+    }
+    private boolean isLeap(int y){
+      if(y % 4 != 0) return false;
+      else if(y%100 != 0) return true;
+      else if(y % 400 != 0) return false;
+      else return true;
+    }
+}
diff --git a/Easy/Fibonacci Numbers.java b/Easy/Fibonacci Numbers.java
@@ -1,26 +1,20 @@
 class Solution {
-    int[] arr;
-    public int fib(int N) {
-        arr = new int[N + 1];
-        return fibHelper(N);
+  public int fib(int N) {
+    Integer[] memo = new Integer[N + 1];
+    return getFib(memo, N);
+  }
+  
+  private int getFib(Integer[] memo, int N) {
+    if (memo[N] != null) {
+      return memo[N];
     }
-    
-    private int fibHelper(int N) {
-        if (N == 0) {
-            return 0;
-        }
-        
-        if (N == 1) {
-            arr[1] = 1;
-            return 1;
-        }
-        
-        if (arr[N] != 0) {
-            return arr[N];
-        }
-        
-        arr[N] = fibHelper(N - 1) + fibHelper(N - 2);
-        
-        return arr[N];
+    else if (N == 0) {
+      return 0;
     }
+    else if (N == 1) {
+      return 1;
+    }
+    memo[N] = getFib(memo, N - 1) + getFib(memo, N - 2);
+    return memo[N];
+  }
 }
diff --git a/Easy/Implement Queue using Stacks.java b/Easy/Implement Queue using Stacks.java
@@ -1,37 +1,46 @@
 class MyQueue {
 
-    /** Initialize your data structure here. */
-    Stack<Integer> oldStack = new Stack<>();
-    Stack<Integer> newStack = new Stack<>();
-    
-    /** Push element x to the back of queue. */
-    public void push(int x) {
-        while (!newStack.isEmpty()) {
-            oldStack.push(newStack.pop());
-        }
-        oldStack.push(x);
+  /** Initialize your data structure here. */
+  Stack<Integer> stack;
+  Stack<Integer> revStack;
+  public MyQueue() {
+    stack = new Stack<>();
+    revStack = new Stack<>();
+  }
+
+  /** Push element x to the back of queue. */
+  public void push(int x) {
+    stack.push(x);
+  }
+
+  /** Removes the element from in front of queue and returns that element. */
+  public int pop() {
+    while (!stack.isEmpty()) {
+      revStack.push(stack.pop());
     }
-    
-    /** Removes the element from in front of queue and returns that element. */
-    public int pop() {
-        while (!oldStack.isEmpty()) {
-            newStack.push(oldStack.pop());
-        }
-        return newStack.pop();
+    int num = revStack.pop();
+    while (!revStack.isEmpty()) {
+      stack.push(revStack.pop());
     }
-    
-    /** Get the front element. */
-    public int peek() {
-        while (!oldStack.isEmpty()) {
-            newStack.push(oldStack.pop());
-        }
-        return newStack.peek();
+    return num;
+  }
+
+  /** Get the front element. */
+  public int peek() {
+    while (!stack.isEmpty()) {
+      revStack.push(stack.pop());
     }
-    
-    /** Returns whether the queue is empty. */
-    public boolean empty() {
-        return oldStack.isEmpty() && newStack.isEmpty();
+    int num = revStack.peek();
+    while (!revStack.isEmpty()) {
+      stack.push(revStack.pop());
     }
+    return num;
+  }
+
+  /** Returns whether the queue is empty. */
+  public boolean empty() {
+    return stack.isEmpty();
+  }
 }
 
 /**
