7-113 3204 校门外的树木

#include <algorithm>
#include <cstdint>
#include <iostream>
#include <limits>
#include <numeric>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>

using i32 = std::int32_t;
using i64 = std::int64_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;
using pii = std::pair<i32, i32>;
using pll = std::pair<i64, i64>;
using vi = std::vector<i32>;
using vll = std::vector<i64>;
using vpii = std::vector<pii>;
using vpll = std::vector<pll>;

void solve();

int main()
{
    std::cin.tie(nullptr)->sync_with_stdio(false);
    solve();
}

void solve()
{
    i32 l, m;
    std::cin >> l >> m;
    vi array(l + 1, 1);
    for (i32 i = 1; i <= m; ++i)
    {
        i32 l, r;
        std::cin >> l >> r;
        for (i32 j = l; j <= r; ++j)
        {
            --array[j];
        }
    }
    i32 count = 0;
    for (i32 i = 0; i <= l; ++i)
    {
        if (array[i] == 1)
        {
            ++count;
        }
    }
    std::cout << count;
}

暴力大法好！