Data structure and algorithm-two points lookup

Concept

Binary search, also known as binary lookup, is a highly efficient method of finding. It has a time complexity of O (LOGN)

Two-point lookup requirements: ordered linear table

Basic ideas

The basic idea of binary search is to divide the current search interval, and the range of the interval is narrowed down one step at a time, if a direct return is found, and the reverse is stopped until the interval has only one element.

Realize

Set R as an ordered linear table with a value increment

Implementation steps:

• First determine the midpoint position of the interval: mid=[(Low+high)/2]
• Then compare the value of the key to R[mid]: if it is equal, return to the current mid directly, otherwise determine the new interval operation, which is divided into two cases

①r[mid]>key indicates that key is on the left side of the interval, so low is constant, high=mid-1

②r[mid]<key indicates that key is on the right side of the interval, so high is constant, low=mid+1

• Returns 1 if not found

Code implementation:

        public int Binsearch (int[] array, int key)        {            int. = 0, high = array. Length-1, mid;            while (low <= high)            {                mid = (low + high)/2;                int curvalue = Array[mid];                if (Curvalue = = key)                    return mid;                if (Curvalue > key)                {high                    = mid-1;                }                else                {Low                    = mid + 1;                }            }            return-1;        }

Data structure and algorithm-two points lookup