vector在oj和IDE上的区别:

周赛37 T2 截断数组

cout << "front capcity : " << front.capacity() << " size : " << front.size() << endl;
cout << "back capcity : " << back.capacity() << " size : " << back.size() << endl;

样例:
5
1 3 1 1 4

IDE(clion):
front capcity : 4 size : 4
back capcity : 4 size : 3

OJ(acwing):
front capcity : 8 size : 5
back capcity : 8 size : 5

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

typedef long long ll;
using namespace std;

const int maxn = 2e5 + 5;
ll n, sum = 0;
ll num[maxn]{0};
vector<ll> front, back;


int main()
{
    cin >> n;
    front.push_back(0ll);
    back.push_back(0ll);
    for (int i = 1; i <= n; i++)
    {
        scanf("%lld", &num[i]);
        sum += num[i];
    }
    ll t = sum / 2;
    bool m1 = true, m2 = true;
    for (int i = 1; i <= n; i++)
    {
        //注意vector的size!
        if(m1)
        {
            if (front[i - 1] + num[i] <= t)
            {
                front.push_back(front[i - 1] + num[i]);
            }
            else
            {
                m1 = false;
            }
        }
        if(m2)
        {
            if (back[i - 1] + num[n - i + 1] <= t)
            {
                back.push_back(back[i - 1] + num[n - i + 1]);
            }
            else
            {
                m2 = false;
            }
        }
    }
    reverse(front.begin(), front.end());
    reverse(back.begin(), back.end());
    int i = 0, j = 0;
    bool flag = false;
    while (i < front.size() && j < back.size())
    {
        if (front[i] == back[j])
        {
            cout << front[i] << endl;
            flag = true;
            break;
        }
        else if (front[i] > back[j])
        {
            i++;
        }
        else
        {
            j++;
        }
    }
    if (!flag)
    {
        cout << 0 << endl;
    }
    return 0;
}