C++/162_Find_Peak_Element.cpp

Author: xliu45

C/162_Find_Peak_Element.cpp

@@ -0,0 +1,55 @@
+//A peak element is an element that is greater than its neighbors.
+//
+//Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.
+//
+//The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.
+//
+//You may imagine that num[-1] = num[n] = -∞.
+//
+//For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.
+//
+//Author: Xinyu Liu
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+
+class Solution {
+
+public:
+	int findPeakElement(vector<int>& nums) {
+		int sz = nums.size();
+		if (sz == 1)
+			return 0;
+		if (nums.at(0)>nums.at(1)) 
+			return 0;
+		if (nums.at(sz-1)>nums.at(sz-2)) 
+			return sz-1;
+
+		for(int i =1; i<nums.size();i++)
+		{
+			
+			if (nums.at(i-1)<nums.at(i)&nums.at(i)>nums.at(i+1))
+				return i;
+		}
+		return -1;
+
+	}
+};
+
+void main(){
+
+
+	// Initialize vector
+	int myints[] = {1,2,3,4,3};
+	int index;
+	std::vector<int> test (myints, myints + sizeof(myints) / sizeof(int) );
+
+	Solution sol;
+	index = sol.findPeakElement (test);
+
+	printf("%i \n",index);
+
+}