1752. Check if Array Is Sorted and Rotated

Violence

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class Solution {
    public boolean check(int[] nums) {
        int n = nums.length;

        int[] clonedNums = nums.clone();
        Arrays.sort(clonedNums);

        for (int rotateTimes = 0; rotateTimes < n; rotateTimes++) {
            if (arrayEquals(nums, clonedNums, rotateTimes)) {
                return true;
            }
        }

        return false;
    }

    private boolean arrayEquals(int[] nums, int[] clonedNums, int rotateTimes) {
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != clonedNums[safeIndex(i + rotateTimes, nums.length)]) {
                return false;
            }
        }

        return true;
    }

    private int safeIndex(int index, int n) {
        return index % n;
    }
}

Traverse

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class Solution {
    public boolean check(int[] nums) {
        // 如果没有出现下降，则满足条件
        // 如果出现一次下降且末尾元素小于等于起始元素，则满足条件
        // 如果出现多次下降，则不满足条件

        boolean decrease = false;

        for (int i = 1; i < nums.length; i++) {
            if (nums[i] < nums[i - 1]) {
                if (!decrease) {
                    decrease = true;
                } else {
                    return false;
                }
            }
        }

        if (decrease) {
            return nums[nums.length - 1] <= nums[0]; // 注意此处是小于等于，如数组：[6, 10, 6]
        } else {
            return true;
        }
    }
}

References

1752. Check if Array Is Sorted and Rotated