Fix:Peak element in a mountain array

code/algorithm_applications/src/binary_search/peak_element_in_a_mountain_array/peak.c

@@ -0,0 +1,32 @@
+#include <stdio.h>
+
+int findPeakUtil(int arr[], int low, int high, int n)
+{
+    int mid = low + (high - low)/2;  
+
+    if ((mid == 0 || arr[mid-1] <= arr[mid]) &&
+            (mid == n-1 || arr[mid+1] <= arr[mid]))
+        return mid;
+
+
+    else if (mid > 0 && arr[mid-1] > arr[mid])
+        return findPeakUtil(arr, low, (mid -1), n);
+
+
+    else return findPeakUtil(arr, (mid + 1), high, n);
+}
+
+
+int findPeak(int arr[], int n)
+{
+    return findPeakUtil(arr, 0, n-1, n);
+}
+
+
+int main()
+{
+    int arr[] = {1, 3, 20, 4, 1, 0};
+    int n = sizeof(arr)/sizeof(arr[0]);
+    printf("Index of a peak point is %d", findPeak(arr, n));
+    return 0;
+}

code/algorithm_applications/src/binary_search/peak_element_in_a_mountain_array/peak.cpp

@@ -0,0 +1,31 @@
+#include<iostream>
+#include<vector>
+
+using namespace std;
+
+ int peakIndexInMountainArray(std::vector<int>& arr) {
+        int n=arr.size();
+        int s=0;
+        int e = n-1;
+        int mid = s + (e-s)/2;
+        while(s<e){
+            if(arr[mid]<arr[mid+1]){
+                s=mid+1;
+            }
+            else{
+                e=mid;
+            }
+               mid = s + (e-s)/2;
+        }
+        return s;
+    }
+    int main(){
+        vector<int> arr;
+        arr.push_back(0);
+        arr.push_back(1);
+        arr.push_back(4);
+
+
+        int ans = peakIndexInMountainArray(arr);
+        cout<<ans<<endl;
+    }

code/algorithm_applications/src/binary_search/peak_element_in_a_mountain_array/peak.py

@@ -0,0 +1,99 @@
+
+
+
+# the peak element in the array
+def findPeak(arr):
+
+
+	left = 0
+
+
+	right = len(arr) - 1
+
+	while (left < right):
+
+
+		mid = left + (right - left) // 2
+
+
+		if (arr[mid] < arr[(mid + 1)]):
+
+			left = mid + 1
+
+		else:
+
+
+			right = mid
+
+	return left
+
+
+def BS(X, left, right, arr):
+
+	while (left <= right):
+
+		mid = left + (right - left) // 2
+
+		if (arr[mid] == X):
+			return mid
+
+		elif (X > arr[mid]):
+
+			left = mid + 1
+
+		else:
+
+			right = mid - 1
+
+	return -1
+
+def reverseBS(X, left, right, arr):
+
+	while (left <= right):
+
+		mid = left + (right - left) 
+
+		if (arr[mid] == X):
+			return mid
+
+		elif (X > arr[mid]):
+
+			right = mid - 1
+
+		else:
+
+			left = mid + 1
+
+	return -1
+
+def findInMA(X, mountainArr):
+
+	peakIndex = findPeak(mountainArr)
+
+	res = -1
+
+
+	if (X >= mountainArr[0] and
+		X <= mountainArr[peakIndex]):
+
+		res = BS(X, 0, peakIndex, mountainArr)
+
+
+	if (res == -1):
+
+		res = reverseBS(X, peakIndex + 1,
+						mountainArr.size() - 1,
+						mountainArr)
+
+	print(res)
+
+if __name__ == "__main__":
+
+
+	X = 3
+
+	arr = [ 1, 2, 3, 4, 5, 3, 1 ]
+
+	findInMA(X, arr)
+
+