二分法demo

1.python实现

from math import floor

arr = [1, 2, 3, 4, 5, 6, 8, 9, 10, 11]
left = 0
right = len(arr)-1
res = 7

while (left <= right):
    mid = floor((left + right)/2)
    if (arr[mid] < res):
        left = mid + 1
    elif (arr[mid] > res):
        right = mid - 1
    else:
        print(f'找到了，下标为{mid}')
        break

if (left > right):
    print('找不到')

2.c语言实现

#include <stdio.h>

int main()
{

    int arr[10] = {1, 2, 3, 4, 5, 6, 8, 9, 10, 11};
    int res = 8;
    int rz = sizeof(arr) / sizeof(arr[0]);
    int left = 0;
    int right = rz - 1;
    int mid = (rz - 1 + 0) / 2;
    while (left <= right)
    {
        mid = (left + right) / 2;
        if (arr[mid] < res)
        {
            left = mid + 1;
        }
        else if (arr[mid] > res)
        {
            right = mid - 1;
        }
        else
        {
            printf("找到了，下标为：%d\n", mid);
            break;
        }
    }
    if (left > right)
        printf("找不到\n");

    return 0;
}