2012a_82que2

public static int count(int[] a, int x)
    {
        int high = a.length - 1;
        int low = 0;
        int mid, start = -1, end = -1;
        if(a[low] == x)
            start = low;
        if(a[high] == x)
            end = high;
        while(high >= low && start == -1){
            mid = (low + high) / 2;
            if(a[mid] == x)
                if(a[mid - 1] != x)
                    start = mid;
                else
                    high = mid - 1;
            else if(a[mid] < x)
                low = mid + 1;
            else
                high = mid - 1;
        }
        high = a.length - 1;
        low = 0;
        while(high >= low && end == -1){
            mid = (low + high) / 2;
            if(a[mid] == x)
                if(a[mid + 1] != x)
                    end = mid;
                else
                    low = mid + 1;
            else if(a[mid] < x)
                low = mid + 1;
            else
                high = mid - 1;
        }
        if(start == -1)
            return 0;
        return end - start + 1;
    }