1. binary search

FUNCTION binary_search1(arr[], low, high, x):
    WHILE low <= high:  # 持续搜索直到搜索区间无效
        mid = (low + high) >> 1  # 位运算计算中间索引 (等价于/2但更快)
        
        IF arr[mid] == x:        # 找到目标元素
            PRINT "Found at index " + mid
            RETURE
        ELSE IF arr[mid] < x:    # 目标在右半区
            low = mid + 1        # 调整左边界
        ELSE:                    # 目标在左半区
            high = mid - 1       # 调整右边界
    END WHILE
    PRINT "Element not found"    # 搜索空间耗尽未找到
RETURE

# 时间复杂度 O(log n)，空间复杂度 O(1)