算法---索引查找

索引的创建，查找，插入

索引优点

提高数据查询的速度

缺点

需要占用一定磁盘空间，另外减慢了数据的插入和删除速度。

#include<stdio.h>

#define INDEXTABLE_LEN 3
#define TABLE_LEN 30

typedef struct item
{
        int index;
        int start;
        int length;
}INDEXITEM;

long stu[TABLE_LEN] = {1080101,1080102,1080103,1080104,1080105,1080106,0,0,0,0,
                        1080201,1080202,1080203,1080204,0,0,0,0,0,0,
                        1080301,1080302,1080303,1080304,0,0,0,0,0,0};

INDEXITEM indextable[INDEXTABLE_LEN] = {
{10801,0,6},
{10802,10,4},
{10803,20,4}
};
int IndexSearch(int key)
{
        int i,index1,start,length;
        index1 = key /100;
        for(i=0;i<INDEXTABLE_LEN;i++)
        {
                if(indextable[i].index == index1)
                {
                        start = indextable[i].start;
                        length = indextable[i].length;
                        break;
                }
        }
        if(i >= INDEXTABLE_LEN)
        return -1;

        for(i=start;i<start+length;i++)
        {
                if(stu[i] == key)
                        return i;
        }
        return -1;
}

int InsertNode(key)
{
        int i,index1,start,length;
        index1 = key /100;
        for(i=0;i<INDEXTABLE_LEN;i++)
        {
                if(indextable[i].index == index1)
                {
                        start = indextable[i].start;
                        length = indextable[i].length;
                        break;
                }
        }
        for(i=0;i<INDEXTABLE_LEN;i++)
        {
                if(indextable[i].index == index1)
                {
                        start = indextable[i].start;
                        length = indextable[i].length;
                        break;
                }
        }
        if(i >= INDEXTABLE_LEN)
                return -1;
        stu[start+length] = key;
        indextable[i].length++;
        return 0;
}


int main()
{
        long key;
        int i,pos;
        printf("source data:");
        for(i=0;i<TABLE_LEN;i++)
        {
                printf("%ld ",stu[i]);
        }
        printf("\n");
        printf("input search word:");
        scanf("%ld",&key);
        pos = IndexSearch(key);
        if(pos>0)
        printf("search success---%d\n",pos);
        else
        printf("search failed\n");

        printf("input insert word");
        scanf("%ld",&key);
        if(InsertNode(key) == -1)
        printf("insert faild\n");
        else
        {
                for(i=0;i<TABLE_LEN;i++)
                printf("%ld ",stu[i]);
                printf("\n");
        }

        return 0;
}