C++/162_Find_Peak_Element.cpp

C/162_Find_Peak_Element.cpp

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+//162. Find Peak Element
+/*
+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] = -∞.
+
+Example:
+in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.
+
+Tag: Array, Binary Search
+
+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(int argc, char ** argv){
+
+    // 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);
+
+}