solve 162.find-peak-element

Author: andavid

vscode/162.find-peak-element.java

@@ -0,0 +1,65 @@
+/*
+ * @lc app=leetcode id=162 lang=java
+ *
+ * [162] Find Peak Element
+ *
+ * https://leetcode.com/problems/find-peak-element/description/
+ *
+ * algorithms
+ * Medium (41.71%)
+ * Likes:    965
+ * Dislikes: 1468
+ * Total Accepted:    260.6K
+ * Total Submissions: 624.7K
+ * Testcase Example:  '[1,2,3,1]'
+ *
+ * A peak element is an element that is greater than its neighbors.
+ *
+ * Given an input array nums, where nums[i] ≠ nums[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 nums[-1] = nums[n] = -∞.
+ *
+ * Example 1:
+ *
+ *
+ * Input: nums = [1,2,3,1]
+ * Output: 2
+ * Explanation: 3 is a peak element and your function should return the index
+ * number 2.
+ *
+ * Example 2:
+ *
+ *
+ * Input: nums = [1,2,1,3,5,6,4]
+ * Output: 1 or 5
+ * Explanation: Your function can return either index number 1 where the peak
+ * element is 2,
+ * or index number 5 where the peak element is 6.
+ *
+ *
+ * Note:
+ *
+ * Your solution should be in logarithmic complexity.
+ *
+ */
+class Solution {
+  public int findPeakElement(int[] nums) {
+    int low = 0;
+    int high = nums.length - 1;
+    while (low < high) {
+      int mid1 = low + (high - low) / 2;
+      int mid2 = mid1 + 1;
+      if (nums[mid1] < nums[mid2]) {
+        low = mid2;
+      } else {
+        high = mid1;
+      }
+    }
+    return low;
+  }
+}
+