solve #162

Author: aylei

src/lib.rs

@@ -150,3 +150,4 @@ mod n0152_maximum_product_subarray;
 mod n0153_find_minimum_in_rotated_sorted_array;
 mod n0154_find_minimum_in_rotated_sorted_array_ii;
 mod n0155_min_stack;
+mod n0162_find_peak_element;

src/n0162_find_peak_element.rs

@@ -0,0 +1,64 @@
+/**
+ * [162] Find Peak Element
+ *
+ * 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.
+ * 
+ */
+pub struct Solution {}
+
+// submission codes start here
+
+impl Solution {
+    pub fn find_peak_element(nums: Vec<i32>) -> i32 {
+        let (mut lo, mut hi) = (0_usize, nums.len() - 1);
+        let mut mid = 0;
+        while lo < hi {
+            mid = (hi - lo) / 2 + lo;
+            if mid + 1 < nums.len() && nums[mid] < nums[mid+1]{
+                lo = mid + 1;
+            } else {
+                hi = mid;
+            }
+        }
+        lo as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_162() {
+        assert_eq!(Solution::find_peak_element(vec![1,2,3,1]), 2);
+        assert_eq!(Solution::find_peak_element(vec![1,2,1,3,5,6,4]), 5);
+    }
+}