Question

我正在为我的动态数组类编写一个多搜索算法，并且我的实现尝试了二进制搜索，但我的程序不会正确设置我的整数mid的值。

以下是该方法的代码：

public static boolean search(int[] array, int value) {
    int first = 0, last = array.length - 1, mid = ((first + last) / array.length);
    System.out.println(first + " - " + mid + " - " + last);
    while(true) {
        System.out.println(first + " - " + mid + " - " + last);
        if (value == array[mid]) {return true;}
        if (first == last || mid == last || mid == first) {return false;}

        if (value > array[mid]) {
            first = mid;
            mid = (first + last) / (last + 1);
        }
        if (value < array[mid]) {
            last = mid;
            mid = (first + last) / (last + 1);
        }
        System.out.println(first + " - " + mid + " - " + last);
    }
}

我使用数百个测试运行程序，但mid的值始终为0（输出为0 - 0 - 111725或0 - 0 - 127或0 - 0 - 15）。非常感谢所有帮助！

Answer 1

不应该＆＃39; T：

mid = ((first + last) / array.length)

......实际上是这样的

mid = ((first + last) / 2)

...而是让你获得mid？

要获得2个值之间的中间值，您需要添加值 并除以2 。

Answer 2

确保您的数组升序顺序：

public static boolean search(int[] array, int value) {
    int first = 0, last = array.length - 1, mid = ((first + last) / 2); //Divide by 2
    System.out.println(first + " - " + mid + " - " + last);
    while(true) {
        System.out.println(first + " - " + mid + " - " + last);
        if (value == array[mid]) {return true;}
        if (first == last || mid == last || mid == first) {return false;}

        if (value > array[mid]) {
            first = mid;
            mid = (last + first) / 2; //Divide by 2
        }
        if (value < array[mid]) {
            last = mid;
            mid = (first + last) / 2; //Divide by 2
        }
        System.out.println(first + " - " + mid + " - " + last);
    }
}

二进制搜索无法正常运行

2 个答案: