二分查找的 上边界和下边界 以及最接近上边界和最接近下边界的例子

Posted 2020-12-11 itdef

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// 23132423543426561213.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//

#include <iostream>
#include <vector>


using namespace std;


int test1[] = {1,3,5,5,5,5,5,5,5,11,12,16,99,100};
int test2[] = { 1,1,2,2,3,3,3,3,4,7,8,8,9,9,9,9,11,12,14,18,99,100 };


void fun1(int arr[],int len )
{
    int l = 0; int r = len - 1;

    while (l < r) {
        int mid = l + r >> 1;
        if (arr[mid] >= 5) r = mid;
        else l = mid + 1;
    }
    cout << "l = " << l << ".r = " << r << ". arr[l] = " << arr[l] << ". arr[r] = " << arr[r] << endl;


    l = 0; r = len  - 1;;

    while (l < r) {
        int mid = (l + r + 1) >> 1;
        if (arr[mid] <= 5) l = mid;
        else r = mid - 1;
    }

    cout << "l = " << l << ".r = " << r << ". arr[l] = " << arr[l] << ". arr[r] = " << arr[r] << endl;

}


int main()
{
    //fun1(test1,sizeof(test1)/sizeof(test1[0]));

    fun1(test2, sizeof(test2) / sizeof(test2[0]));


    return 0;
}