class Solution {public:    int peakIndexInMountainArray(vector
    
     & A) {        int res=0;        for(int i=0;i
     
       A[res]){                res=i;            }        }        return res;    }};class Solution {public:    int rec(vector
      
       & A, int left, int right){        int mid = (left + right) / 2;        if(mid == 0 || mid == A.size()-2){            if(A[mid] > A[mid+1]){                return mid;            }            else{                return mid+1;            }        }        else{            if(A[mid] > A[mid-1] && A[mid] > A[mid+1]){                return mid;            }            else if(A[mid] > A[mid-1]){                return rec(A, mid, right);            }            else if(A[mid] < A[mid-1]){                return rec(A, left, mid-1);            }        }    }    int peakIndexInMountainArray(vector
       
        & A) {        return rec(A, 0, A.size()-1);    }};