LC-34

package getSecondBiggestNum.nums;

public class LC34 {
    public int[] searchRange(int[] nums, int target) {
        int temp = binarySearch(nums, target);
        int[] ints = new int[]{-1, -1};

        if (temp == -1) {
            return ints;
        } else if (nums.length <= 2) {
            //pass
        } else if (nums[temp - 1] == target) {
            ints[0] = temp - 1;
            ints[1] = temp;
            return ints;
        } else if (nums[temp + 1] == target) {
            ints[0] = temp;
            ints[1] = temp + 1;
            return ints;
        }
        return ints;
    }

    /**
     * @param nums
     * @param target
     * @return
     */
    public int binarySearch(int[] nums, int target) {
        int left = 0;
        int right = nums.length - 1;
        while (left <= right) {
            int middle = left + ((right - left) / 2);
            if (nums[middle] < target) {
                left = middle + 1;
            } else if (nums[middle] > target) {
                right = middle - 1;
            } else {
                return middle;
            }
        }
        return -1;
    }
}

注意：pass部分，在 nums[ ] 元素少于等于俩个的时候会有多种”意外“。

容易混淆自己。

一个二分来查找左右边界，很容易把自己绕进去，建议扎扎实实的写两个二分分别找左边界和右边界。

class Solution {
    int[] searchRange(int[] nums, int target) {
        int leftBorder = getLeftBorder(nums, target);
        int rightBorder = getRightBorder(nums, target);
        // 情况一
        if (leftBorder == -2 || rightBorder == -2) return new int[]{-1, -1};
        // 情况三
        if (rightBorder - leftBorder > 1) return new int[]{leftBorder + 1, rightBorder - 1};
        // 情况二
        return new int[]{-1, -1};
    }

    int getRightBorder(int[] nums, int target) {
        int left = 0;
        int right = nums.length - 1;
        int rightBorder = -2; // 记录一下rightBorder没有被赋值的情况
        while (left <= right) {
            int middle = left + ((right - left) / 2);
            if (nums[middle] > target) {
                right = middle - 1;
            } else { // 寻找右边界，nums[middle] == target的时候更新left
                left = middle + 1;
                rightBorder = left;
            }
        }
        return rightBorder;
    }

    int getLeftBorder(int[] nums, int target) {
        int left = 0;
        int right = nums.length - 1;
        int leftBorder = -2; // 记录一下leftBorder没有被赋值的情况
        while (left <= right) {
            int middle = left + ((right - left) / 2);
            if (nums[middle] >= target) { // 寻找左边界，nums[middle] == target的时候更新right
                right = middle - 1;
                leftBorder = right;
            } else {
                left = middle + 1;
            }
        }
        return leftBorder;
    }
}