Cometitive-coding-10-complete

problem1.java

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+// Time Complexity :O(n)
+// Space Complexity :O(1)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this :no
+
+/*
+Approach
+idea here is to buy only if the next day the price goes up 
+single pass as we are only deal this the next ele to i 
+*/
+
+class Solution {
+    public int maxProfit(int[] prices) {
+        int total = 0;
+        for (int i = 0; i < prices.length - 1; i++) {
+            if (prices[i] < prices[i + 1]) {
+                total += prices[i + 1] - prices[i];
+            }
+        }
+        return total;
+    }
+}

problem2.java

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+// Time Complexity :O(1)
+// Space Complexity :O(1)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this :no
+
+/*
+Approach
+we are using a native iterator to implement this iterator,
+you native iterator is alway one ele ahead of the peeking iterator
+
+when the peeking iterator is initialised we store the first ele 
+
+if peek it called we just return the value of the stored ele
+
+if next is called, as we alreay have the next value stored in ele we return that value but 
+before we return we check if there is a next ele if yes we save that
+
+if hasnext it checks if nextEl is null or not, and returns accordingly 
+*/
+
+class PeekingIterator implements Iterator<Integer> {
+    Iterator<Integer> iter;
+    Integer nextEl;
+
+    public PeekingIterator(Iterator<Integer> iterator) {
+        this.iter = iterator;
+        this.nextEl = iter.next();
+    }
+
+    public Integer peek() {
+        return nextEl;
+    }
+
+    @Override
+    public Integer next() {
+        Integer temp = nextEl;
+        nextEl = null;
+        if (iter.hasNext()) {
+            nextEl = iter.next();
+        }
+        return temp;
+    }
+
+    @Override
+    public boolean hasNext() {
+        if (nextEl != null) {
+            return true;
+        }
+        return false;
+    }
+}