二分查找

本文已参与「新人创作礼」活动，一起开启掘金创作之路。

二分查找，最常用的查找方式，但是在写代码的时候有许多细节需要注意。

• low <= high or low < high
• mid = (left + right) / 2 or mid = left + (right - left) / 2

看一下官方的写法

// Like public version, but without range checks.
    private static int binarySearch0(long[] a, int fromIndex, int toIndex, long key) {
        int low = fromIndex;
        int high = toIndex - 1;

        while (low <= high) {
        	// >>>表示无符号右移 
            int mid = (low + high) >>> 1;
            long midVal = a[mid];

            if (midVal < key)
                low = mid + 1;
            else if (midVal > key)
                high = mid - 1;
            else
                return mid; // key found
        }
        return -(low + 1);  // key not found.
    }