class Solution { public: int minNumberInRotateArray(vector<int> arr) { if (arr.empty()) return 0; int num = arr.size(); int l = 0, r = num-1; while(r>l){ int cen = (l+r)/2; if (arr[cen]>arr[r]){ l = cen+1; } else{ r = cen; } } return arr[l]; } };