LeetCode – Refresh – Find Minimum in Rotated Array

Be carefully with one element and two element sitution.

1. Since mid = (start + end) / 2 is alway shifting to the left. So when we do comparision, not use num[mid] > num[start] but num[mid] > num[end].

2. We need find the minimum, So when we are closing to the minimum, we need get start = mid + 1 and end = mid as offset for left shifting.

 

class Solution {
public:
    int findMin(vector<int> &num) {
        int start = 0, end = num.size()-1, mid = 0;
        if (num[start] < num[end]) return num[start];
        while (start < end) {
            mid = (start + end)/2;
            if (num[mid] > num[end]) {
                start = mid + 1;
            } else {
                end = mid;
            }
        }
        return num[start];
    }
};