数据结构之二分查找

• 实现一个有序数组的二分查找算法
• 实现模糊二分查找算法（比如大于等于给定值的第一个元素）

实现一个有效数组的二分查找算法

#include <stdio.h>

int binary_search(int arr[],int key,int sz)
{
    int mid = 0;
    int left = 0;
    int right = sz - 1;
    while (left <= right)
    {
        int mid = left + (right - left) / 2;
        if (arr[mid] < key)
            left = arr[mid] + 1;
        else if (arr[mid] > key)
            right = arr[mid] - 1;
        else
            return mid;
    }
    return -1;
}
int main()
{
    int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int sz = sizeof(arr) / sizeof(arr[0]);
    int key = 7;
    int ret = binary_search(arr, key, sz);
    if (ret == -1)
        printf("找不到!\n");
    else
        printf("找到了!下标为:%d\n", ret);
    return 0;
}

实现模糊二分查找算法（比如大于等于给定值的第一个元素）

class Solution(object):
    def mySqrt(self, x):
        if x==1 or x==0:
            return x
        else:
            left=0
            right=x
            while left<right:
                temp=(left+right)/2
                if int(temp)**2<=x and int((temp+1))**2>=x:                
                    if int((temp+1))**2==x:
                        temp=int((temp+1))
                    return(int(temp))
                    break        
                elif int(temp)**2<x and int(temp+1)**2<x:
                    left=temp             
                else:
                    right=temp