An array is called centered-15 if some consecutive sequence of elements of the array sum to 15 and this sequence is preceded and followed by the same number of elements.

美国面试题12

1.题目：

An array is called centered-15 if some consecutive sequence of elements of the array sum to 15 and this sequence is preceded and followed by the same number of elements. For example
{3, 2, 10, 4, 1, 6, 9} is centered-15 because the sequence 10, 4, 1 sums to 15 and the sequence is preceded by two elements (3, 2) and followed by two elements(6,9).
Write a method called isCentered15 that returns 1 if its array argument is centered-15, otherwise it returns 0.
If you are programming in Java or C#, the function prototype is
int isCentered15(int[ ] a)
If you are programming in C++ or C, the function prototype is
int isCentered5(int a[ ], int len) where len is the number of elements in the array.

2. 测试样例

3. java实现代码:

public class Centered15 {
    public static void main(String[] args) {
//        int a[] = {3,2,10,4,1,6,9};
//        int a[] = {2,10,4,1,6,9};
//        int a[] = {3,2,10,4,1,6};
//        int a[] = {1,1,8,3,1,1};
//        int a[] = {9,15,6};
//        int a[] = {1,1,2,2,1,1};
        int a[] = {1,1,15,-1,-1};
        System.out.println(isCentered15(a));
    }

    public static int isCentered15(int[] a){

        int length = a.length;
        if(length==0){
            return 0;
        }else if(length==3 && a[1]==15){
            return 1;

        }

        int x =1;
        while (x!=length-2) {

            int sum = 0;
            for (int i = x; i < length - 1; i++) {

                sum = sum + a[i];


//                System.out.println("x=" + x);

                if (sum == 15) {
                    //记录 x,i, 判断是不是中间
                    System.out.println("i=" + i+"sum="+sum+"x="+x);
                    if(length-i-1 == x) {
                        return 1;
                    }
                }
            }
            x ++;

        }
        return 0;

    }
}