正常的二分查找，头尾不断替换，每次砍掉一半

#define _CRT_SECURE_NO_WARNINGS
#include<stdlib.h>
#include<stdio.h>
#define N 1024

void search(int a[N],int num) //二分查找法
{
    int tou = 0;
    int wei = N - 1;
    int zhong;
    int flag = -1;  
    int ci = 0;
    while (tou<=wei)
    {    
        zhong = (tou + wei) / 2;
        if (num==a[zhong]) 
        {    
            ci++;
            printf("找到，a[%d]=%d", zhong, num);
            flag = 1;
            break;
        }
        else if (num > a[zhong])
        {
            tou = zhong + 1;
        }
        else 
        {
            wei = zhong - 1;
        }

    }

    if (flag == -1)
    {
        printf("没有找到");
    }
}

拉格朗日二分查找，每次砍掉一大半

void searchL(int a[N], int num) //拉格朗日查找法
{
    int tou = 0;
    int wei = N - 1;
    int zhong;
    int flag = -1;
    int ci = 0;
    while (tou <= wei)
    {
        zhong = tou+(wei-tou)*1.0*(num-a[tou])/(a[wei]-a[tou]);
        if (num == a[zhong])
        {
    
            printf("找到，a[%d]=%d,%d", zhong, num,++ci);
            flag = 1;
            break;
        }
        else if (num > a[zhong])
        {
            tou = zhong + 1;
        }
        else
        {
            wei = zhong - 1;
        }

    }

    if (flag == -1)
    {
        printf("没有找到");
    }
}
void main()
{
    int a[N];
    for (int i = 0; i < N; i++)
    {
        a[i] = i;
        printf("%d", i);
    }

    int num;
    scanf("%d", &num);
    searchL(a, num);
    system("pause");
}

二分查找