Sequential Table Lookup algorithm

Sequential table lookup algorithm is the most basic searching technique in the algorithm.

Algorithm principle: In layman's terms, look up data from a table and return the current value index whenever you see the same data as the value you are taking.

On the code:

public  int  seqserch (int []a, int key) {
	int i,n=a.length;
	for (i = 1; i < n; i++) {
            if (a[i] = = key) {
	        return i;
	     }}
}

The code is simple, but when multiple threads or concurrent requests are encountered, the value of I may be out of bounds. So, the program community has a

Well-known Sentinel mode, here is the rewritten code:

public int Seq_serch (int []a, int key) {

	int i;
	A[0] = key;//Sentinel
	i = a.length//starts from the tail
	while (a[i]! = key) {
	     i--;
	}
	Return i;//if return 0 fails to find
}

Summary: Sequential lookup technology is extremely inefficient when it encounters a very large range of lookups. Sentinel mode is recommended when there is a small amount of data available.