版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Somnus_k/article/details/82781376
思路：二分查找找到目标值，然后从目标值左右分别进行搜索，如果和目标值相同，则更新下标，否则结束（因为有序）。
public class FindFirstandLastPositionofElementinSortedArray34 {
public static void main(String[] args) {
int num[] = { 5, 7, 7, 8, 8, 10 };
System.out.println(Arrays.toString(searchRange(num, 8)));
System.out.println(Arrays.toString(searchRange(num, 10)));
System.out.println(Arrays.toString(searchRange(num, 5)));
System.out.println(Arrays.toString(searchRange(num, 2)));
}
public static int[] searchRange(int[] nums, int target) {
int mid = search(nums, target);
int[] t = new int[] { mid, mid };
if(mid==-1)
return t;
int tmp = mid - 1;
while (tmp >= 0)
if (nums[tmp] == nums[mid])
{
t[0] = tmp;
tmp--;
}
else
break;
tmp = mid + 1;
while (tmp < nums.length)
if (nums[tmp] == nums[mid])
{
t[1] = tmp;
tmp++;
}
else
break;
return t;
}
private static int search(int[] nums, int target) {
int low = 0;
int high = nums.length - 1;
int mid = 0;
while (low <= high) {
mid = (low + high) / 2;
if (nums[mid] > target)
high = mid - 1;
else if (nums[mid] < target)
low = mid + 1;
else
return mid;
}
return -1;
}
}
输出：
