珠心算测验（ACM）

python3做法：

n = int(input())
lst= list(map(int,input().split()))
times = []
for i in lst:
    for j in lst:
        if i < j and i + j in lst and i+j not in times:
            times.append(i+j)
print(len(times))

c语言做法

#include<stdio.h>
int main()
{
    int n, i, j, k, count = 0, temp;
    scanf("%d", &n);
    int a[101] = {0};
    int b[101] = {0};
    for (i = 0; i < n; i++) //输入
    {
        scanf("%d", &a[i]);
        b[i] = a[i];
    }

    for (i = 0; i < n - 1; i++) //排序
    {
        for (j = 0; j < n - 1 - i; j++)
        {
            if (a[j] > a[j + 1])
            {
                temp = a[j];
                a[j] = a[j + 1];
                a[j + 1] = temp;
            }
        }
    }   

    for (i = 0; i < n; i++)
    {
        for (j = i + 1; j < n; j++)
        {
            temp = a[i] + a[j];
            for (k = 0; k < n; k++)
            {
                if (temp == b[k])
                {
                    count++;
                    b[k] = 0;
                    continue;
                }
            }
        }
    }
    printf("%d\n", count);
    return 0;
}

c++做法：

#include<iostream>
#include<algorithm>
#include"vector"
using namespace std;
/* int exist(int temp, vector<int> &vec) //判断temp是否在vec 中存在 { auto it = find(vec.begin(), vec.end(), temp); if (it != vec.end()) //查找成功 { vec.erase(it); return 1; } else return 0; } */

int exist(int temp, vector<int>& vec)
{
    for(vector<int>::iterator it = vec.begin(); it != vec.end(); it++)
    {
        if (temp == *it)
        {
            *it = 0;    //把已经确定的数等于0,防止重复
            return 1;
        }
    }
    return 0;
}

int main()
{
    vector<int> vec1, vec2;
    int n = 0, count = 0;
    cin >> n;
    while (n--)
    {
        int t = 0;
        cin >> t;
        vec1.push_back(t);
    }
    sort(vec1.begin(), vec1.end()); //在algorithm中
    vec2 = vec1;
    for (auto it = vec1.begin(); it != vec1.end(); it++)
    {
        for (auto it2 = it + 1; it2 != vec1.end(); it2++)
        {
            auto temp = *it + *it2;
            if (exist(temp, vec2))
            {
                count++;
            }
        }   
    }
    cout << count << endl;
    return 0;
}