shz.core.alg.search.BinarySearcher Maven / Gradle / Ivy

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${project.artifactId}

There is a newer version: 2024.0.2

package shz.core.alg.search;

public final class BinarySearcher {
    private BinarySearcher() {
        throw new IllegalStateException();
    }

    /**
     * 二分查找，数组a为升序数组
     * 时间复杂度：log2(n)
     *
     * @return 返回key在数组a中的索引
     */
    public static int search(int[] a, int k) {
        int lo = 0, hi = a.length - 1;
        while (lo <= hi) {
            int mid = lo + (hi - lo) / 2;
            if (k < a[mid]) hi = mid - 1;
            else if (k > a[mid]) lo = mid + 1;
            else return mid;
        }
        return -1;
    }
}