Search for a Range(Medium)

Given a sorted array of integers, find the starting and ending position of a given target value.

Your algorithm's runtime complexity must be in the order of O(log n).

If the target is not found in the array, return [-1, -1].

For example, Given [5, 7, 7, 8, 8, 10] and target value 8,

return [3, 4].

Java代码

public int[] searchRange(int[] A, int target) {
    int[] ret = {-1, -1};
    int start = 0;
    int end = A.length - 1;
    while (start < end) {
        int mid = (start + end) / 2;
        if (A[mid] < target)
            start = mid + 1;
        else
            end = mid;
    }

    int low;
    if (A[start] != target)
        return ret;
    else
        low = start;
    start = 0;
    end = A.length - 1;
    while (start < end) {
        int mid = (start + end) / 2;
        if (A[mid] < target + 1)
            start = mid + 1;
        else
            end = mid;
    }
    int high = A[start] == target ? start : start - 1;

    ret[0] = low;
    ret[1] = high;
    return ret;
}