查找最大

Question

我想从整数列表中找到最大的数字。 例如，如果输入= (-10, -47, 3, 4,100,12,200,1)，则最大数量为200，我想要找到的数字为100。

这是我的程序，

template<typename T>
T MaxElem(T t, T s)
{
    return std::max(t, s);
}
template<typename T, typename ...A>
T MaxElem(T a, T b, A...x)
{
    return MaxElem(MaxElem(a,b), x...);
}
template<typename T>
T Second(T t1, T t2)
{
    return (t1 < t2)? t2 : t1;
}
template<typename T>
T Second(T t1, T t2, T x)
{
    return (t1 < t2) ? ((t2 == x)? t1 : t2) : t1;
}
template<typename T, typename ...args>
T Second(T t1, T t2, args...a)
{   
    return Second(Second(t1, t2, MaxElem(t1, t2, a...)), a...);
}

输出200作为错误结果。

Answer 1

我认为下面有一个简单的方法：

std::sort(numbers.begin(), numbers.end());
std::reverse(numbers.begin(), numbers.end());
cout << numbers[1] ; // second largest 

Answer 2

你的第二个需要调整：

string sql = @"INSERT INTO CC_MSD_LIMS_STAGING (SMN, FACILITY_ID,SCHEDULE_DATE, IND_NAME, ADDRESS_LINE_1, ADDRESS_LINE_2, CITY, STATE, ZIP, SMPL_PT_DESC, SMPL_PT_NUM, SPLIT, TRUCK_ID, PROJECT_TYPE, SAMPLER, IND_ID, BOTTLE_TYPE, PRESERVATIVE, SAMPLE_TYPE, POLLUTANT, UNITS, SIU_IND, SURCHARGE_IND, SPECIAL_INSTRUCTIONS, AUTOSAMPLER_READY, SHIFT_L, SHIFT_START_TIME, PRIMARY_CONTACT_FIRSTNAME, PRIMARY_CONTACT_LASTNAME, PRIMARY_CONTACT_PHONE, ALTERNATE_CONTACT_FIRSTNAME, ALTERNATE_CONTACT_LASTNAME, ALTERNATE_CONTACT_PHONE, MONITORING_ID) 
VALUES ('1793175', '1037247400', '11/13/2017 12:00:00 AM', 'STONETRENDS LLC', '18092 Chesterfield Airport', '', 'Chesterfield', 'MO', '63005', '6"" PVC vent 140'' S, 4'' W of NW crnr of bldg', '001', 'N', '493', 'IM', 'M', '2464', 'P0', 'None', 'T04', 'T208000', 'mg/L', '', 'Y', '', 'Y', '1', '0700AM', 'Patrick ', 'Martin', '6365371607', 'Stefan ', 'Landgraf', '6365371607', '-1')";

返回#include <algorithm> template<typename T> T MaxElem(T t, T s) { return std::max(t, s); } template<typename T, typename ...A> T MaxElem(T a, T b, A...x) { return MaxElem(MaxElem(a, b), x...); } template<typename T> T Second(T t1, T t2) { return (t1 < t2) ? t1 : t2; //here } template<typename T> T Second(T t1, T t2, T x) { return Second(t1, x) < Second(t2, x) ? (t2 == x ? t1 : t2) : (t1 == x ? t2 : t1); //and here } template<typename T, typename ...args> T Second(T t1, T t2, args...a) { return Second(Second(t1, t2, MaxElem(t1, t2, a...)), a...); } int main() { std::cout << Second(-10, -47, 3, 4, 100, 12, 200); return 0; }

Answer 3

您可以使用std::nth_element功能：

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>

int main() {
    std::vector<int> numbers{ -10, -47, 3, 4, 100, 12, 200, 1 };
    std::nth_element(numbers.begin(), numbers.begin() + 1, numbers.end(), std::greater<int>());
    std::cout << "The second largest element is " << numbers[1] << '\n';
}