【查找】二分查找

二分查找，也称为折半查找

/** * 二分查找，折半查找 * @param arr 有序数组 * @param key 关键字 * @return 关键字在数组中的下标 */public int binsearch(int[] arr, int key){    int low = 0;    int high = arr.length-1;    while(low <= high){        int mid = (low + high) / 2;        if (arr[mid] == key) return mid;        else if (arr[mid] < key) low = mid + 1;        else if (arr[mid] > key) high = mid - 1;    }    return -1;}