【二分查找】及相关问题

1.旋转数组中找最小值

顺序查找时间复杂度为O(n),二分查找时间复杂度为O(logn)

// rotateArrMin.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
using namespace std;

void MinInOrder(int *arr,int begin,int end)
{
    int result = arr[begin];
    for(int i = begin+1; i < end;i++)
        result = min(result,arr[i]);
    cout<<result<<endl;
}

void Min(int* arr,int len)
{
    if(arr == NULL || len <= 0)
        return;

    int begin = 0;
    int end = len - 1;
    int middle = begin;
    int result = 0;
    //强middle初始化为begin,在原数组中也能返回第一个数即最小值,(此时旋转了0)
    while(begin <= end)
    {
        if(end - begin == 1)
        {
            result = arr[end];
            break;
        }
        middle = (begin + end)>>1;

        if(arr[begin] == arr[middle] && arr[middle] == arr[end])
            MinInOrder(arr,begin,end);
        //处理01111的旋转，11101等

        if(arr[middle] >= arr[begin])
            begin = middle;
        else if(arr[middle] <= arr[end])
            end = middle;
    }
    cout<<result<<endl;
}

int _tmain(int argc, _TCHAR* argv[])
{
    int arr[] = {3,4,5,1,2};
    int len = 5;
    Min(arr,len);
    system("pause");
    return 0;
}