Leetcode 154. Find Minimum in Rotated Sorted Array II

154. Find Minimum in Rotated Sorted Array II

アプローチ

1. 二分探索

class Solution {
    public int findMin(int[] nums) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int start = 0;
        int end = nums.length - 1;

        if (nums[start] < nums[end]) {
            return nums[start];
        }

        while (start < end) {// not putting <= because the array contains unique elements

            int mid = start + (end - start) / 2;

            if (nums[mid] < nums[end]) {
                end = mid;
                // end を利用
            } else if ( nums[mid] > nums[end] ) {
                // right side is rotated, expecting smallest number between mid + 1 <=  end;
                // 5 6 7 8 9 1 2 3
                start = mid + 1;
            } else {
                // reduce duplicate
                // 5 6 7 8 9 1 1 3
                end--;
            }
        }
        return nums[end];
    }
}

2. ソート

class Solution {
    public int findMin(int[] nums) {
        Arrays.sort(nums);
        return nums[0];
    }
}

3. 全体探索

class Solution {
    public int findMin(int[] nums) {
        int min = Integer.MAX_VALUE;
        for (int num : nums) {
            if (num < min)
                min = num;
        }
        return min;
    }
}