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1095-find-in-mountain-array/1095-find-in-mountain-array.cpp

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+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *   public:
+ *     int get(int index);
+ *     int length();
+ * };
+ */
+
+class Solution {
+public:
+    int findInMountainArray(int target, MountainArray &mountainArr) {
+        int n=mountainArr.length();
+        int i=0;
+        int j=n-1;
+        int peak=-1;
+        while(i<=j)
+        {
+            int mid=(i+j)/2;
+            int t=mountainArr.get(mid);
+            if(t>mountainArr.get(mid-1) && t>mountainArr.get(mid+1))
+            {
+                peak=mid;
+                break;
+            }
+            else if(t<mountainArr.get(mid+1) && t>mountainArr.get(mid-1))
+            {
+                i=mid;
+            }
+            else
+            {
+                j=mid;
+            }
+        }
+
+        //in first half
+         i=0;
+         j=peak;
+        while(i<=j)
+        {
+            int mid=(i+j)/2;
+            int t=mountainArr.get(mid);
+            if(t==target)return mid;
+            else if(t<target)
+                i=mid+1;
+            else 
+                j=mid-1;
+        }
+         i=n-1;
+         j=peak;
+        while(j<=i)
+        {
+            int mid=(i+j)/2;
+            int t=mountainArr.get(mid);
+            if(t==target)return mid;
+            else if(t<target)
+                i=mid-1;
+            else 
+                j=mid+1;
+        }
+        return -1;
+    }
+};