2 problems

Author: hitzzc

README.md

@@ -208,6 +208,8 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [279. Perfect Squares](https://github.com/hitzzc/go-leetcode/tree/master/perfect_squares)
 #### [282. Expression Add Operators](https://github.com/hitzzc/go-leetcode/tree/master/expression_add_operators)
 #### [283. Move Zeroes](https://github.com/hitzzc/go-leetcode/tree/master/expression_add_operators)
+#### [284. Peeking Iterator](https://github.com/hitzzc/go-leetcode/tree/master/peeking_iterator)
+#### [287. Find the Duplicate Number](https://github.com/hitzzc/go-leetcode/tree/master/find_the_duplicate_number)
 
 
 

find_the_duplicate_number/find_the_duplicate_number.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+    int findDuplicate(vector<int>& nums) {
+  		int i = 0;
+  		int j = 0;
+  		while (true) {
+  			i = nums[i];
+  			j = nums[nums[j]];
+  			if (i == j) break;
+  		}
+  		j = 0;
+  		while (i != j) {
+  			i = nums[i];
+  			j = nums[j];
+  		}
+  		return i;
+    }
+};

peeking_iterator/peeking_iterator.cpp

@@ -0,0 +1,50 @@
+// Below is the interface for Iterator, which is already defined for you.
+// **DO NOT** modify the interface for Iterator.
+class Iterator {
+    struct Data;
+	Data* data;
+public:
+	Iterator(const vector<int>& nums);
+	Iterator(const Iterator& iter);
+	virtual ~Iterator();
+	// Returns the next element in the iteration.
+	int next();
+	// Returns true if the iteration has more elements.
+	bool hasNext() const;
+};
+
+
+class PeekingIterator : public Iterator {
+	int cache;
+	bool is_peeked;
+public:
+	PeekingIterator(const vector<int>& nums) : Iterator(nums), is_peeked(false) {
+	    
+	}
+
+    // Returns the next element in the iteration without advancing the iterator.
+	int peek() {
+        if (!is_peeked) {
+        	cache = Iterator::next();
+        	is_peeked = true;
+        }
+        return cache;
+	}
+
+	// hasNext() and next() should behave the same as in the Iterator interface.
+	// Override them if needed.
+	int next() {
+		if (is_peeked) {
+			is_peeked = false;
+			return cache;
+		}
+		return Iterator::next();
+	}
+
+	bool hasNext() const {
+	    if (is_peeked) {
+	    	return true;
+	    }
+	    return Iterator::hasNext();
+	}
+};