线性表的三种查找方法：顺序查找、折半查找、分块查找（算法实现）

代码：

#include <iostream>
using namespace std;

#define MAX 20

typedef int KeyType;
typedef int MaxInt;

typedef struct {
	KeyType key;//关键字域
}ElemType;

typedef struct {//顺序表结构类型定义
	ElemType *R;//表基址
	int length;//表长
}SSTable,*Sqlist;//Sequential Search Table

typedef struct {//定义块的结构
	int key;//块中最大值
	int start;//块起始地址
	int end;//块结束地址
}Index_table;
Index_table index_table[4];

//SSTable ST;//定义顺序表ST
void InitList(Sqlist &ST)
{
	ST = (SSTable*)malloc(sizeof(SSTable));//给顺序表分配空间
	ST->R = (ElemType*)malloc(MAX*sizeof(ElemType));
	ST->length = 0;
}
void CreateList(Sqlist &ST)
{
	cout << "请输入线性表长度"<<endl;
	cin >> ST->length;
	cout << "请输入线性表中元素" << endl;
	for (int i = 1; i <= ST->length; i++)
	{
		cin>>ST->R[i].key ;//赋值
	}
}
void Block_Init(Sqlist &ST)
{
	int i, j = 0;
	for (i = 1; i <= 3; i++)
	{
		index_table[i].start = j + 1;//确定每个块的起始值
		j = j + 1;
		index_table[i].end = j + 4;//确定每个块的结束值
		j = j + 4;
		index_table[i].key = ST->R[j].key;//确定每个块范围中元素的最大值
	}
}
int Search_block(Sqlist ST,KeyType key)
{////若成功返回其位置信息，否则返回0
	int i, j;
	i = 1;
	while (i <= 3 && key > index_table[i].key)//确定在哪个块中
		i++;
	if (i > 3)//大于分块数
		return 0;
	j = index_table[i].start;//j=块范围的起始值
	while (j <= index_table[i].end&&ST->R[j].key != key)//在确定块内进行查找
		j++;
	if (j > index_table[i].end)
		j = 0;
	return j;
}
int Search_Seq(Sqlist ST, KeyType key)
{//若成功返回其位置信息，否则返回0
	ST->R[0].key = key;
	int i;
	for ( i = ST->length; ST->R[i].key != key; i--);//这个“；”很重要
	return i;
}

int Search_Bin(Sqlist ST, KeyType key)
{
	int low = 1,high=ST->length;//设置初始区间
	while (low<=high)
	{
		int mid = (low + high) / 2;
		if (ST->R[mid].key == key)return mid;//找到待查元素
		else if (key < ST->R[mid].key)//缩小查找空间
			high = mid - 1;//继续在前半区查找
		else
			low = mid + 1;//继续在后半区查找
	}//while
	return 0;//没找到
}//Search_Bin


int main()
{
	//GraphAdjList *GL = (GraphAdjList*)malloc(sizeof(GraphAdjList));
	//SSTable *ST1 = (SSTable*)malloc(sizeof(SSTable)); 
	Sqlist ST1,ST2,ST3;
	char ch1, ch2;
	int m, n, k;
	int key1, key2, key3;
	char u;//起始点
	ch1 = 'y';
	while (ch1 == 'y')
	{
		cout << "----------线性表的查找----------" << endl;
		cout << "------1.线性表的创建  ------" << endl;
		cout << "------2.顺序查找    ------" << endl;
		cout << "------3.折半查找    ------" << endl;
		cout << "------4.分块查找    ------" << endl;
		cout << "------0.退出          ------" << endl;
		cout << "------请选择菜单号    ------" << endl;
		cin >> ch2;
		getchar();
		cout << endl;
		switch (ch2)
		{
		case'1':
			//顺序表的构建
			cout << "创建第一个无序线性表" <<endl;
			InitList(ST1);
			CreateList(ST1);
			cout << "创建第二个有序线性表" << endl;
			InitList(ST2);
			CreateList(ST2);
			cout << "创建第三个线性表(元素为15个)" << endl;
			InitList(ST3);
			CreateList(ST3);
			Block_Init(ST3);
			break;
		case'2':
			//顺序查找
			cout << "请输入要查找的关键字key1:" << endl;
			cin >> key1;
			m = Search_Seq(ST1, key1);
			if (m == 0) cout << "没找到" << endl;
			else cout << key1 << "的位置为" << m << endl;
			break;
		case'3':
			//折半查找
			cout << "请输入要查找的关键字key2" << endl;
			cin >> key2;
			n = Search_Bin(ST2,key2);
			if (n == 0)cout << "没找到" << endl;
			else cout << key2 << "的位置为" << n << endl;
			break;
		case '4':
			//分块查找
			cout << "请输入要查找的关键字key2" << endl;
			cin >> key3;
			k = Search_block(ST3, key3);
			if (n == 0)cout << "没找到" << endl;
			else cout << key3 << "的位置为" << k << endl;
			break;
		case'0':
			ch1 = 'n';
			break;
		default:
			cout << "输入有误" << endl;

		}//switch

	}//while
	return 0;
}

结果：