描述

给定一个包含 n 个整数的排序数组，找出给定目标值 target 的起始和结束位置。如果目标值不在数组中，则返回[-1, -1]

样例

给出[5, 7, 7, 8, 8, 10]和目标值target=8,
返回[3, 4]

挑战

时间复杂度 O(log n)

代码

public class Solution {
    /*
     * @param A: an integer sorted array
     * @param target: an integer to be inserted
     * @return: a list of length 2, [index1, index2]
     */
    public int[] searchRange(int[] A, int target) {
        if (A == null || A.length == 0) {
            return new int[] {-1, -1};
        }
        
        int startIndex = findStartIndex(A, target);
        int endIndex = findEndIndex(A, target);
        return new int[] {startIndex, endIndex};
    }    
    
    private int findStartIndex(int[] A, int target) {
        int start = 0, end = A.length - 1;
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (A[mid] == target) {
                end = mid;
            }
            if (A[mid] < target) {
                start = mid;
            }
            if (A[mid] > target) {
                end = mid;
            }
        }
        
        if (A[start] == target) {
            return start;
        }
        if (A[end] == target) {
            return end;
        }
        return -1;
    }
    
    private int findEndIndex(int[] A, int target) {
        int start = 0, end = A.length - 1;
        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (A[mid] == target) {
                start = mid;
            }
            if (A[mid] < target) {
                start = mid;
            }
            if (A[mid] > target) {
                end = mid;
            }
        }
        
        if (A[end] == target) {
            return end;
        }
        if (A[start] == target) {
            return start;
        }
        return -1;
    }
}