商品库存管理 参考代码

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
const int maxn = 300000 + 100;
int n, m, cnt0, tmp;
int l[maxn], r[maxn], num[maxn], cnt1[maxn];

int main() {
#ifdef ExRoc
    freopen("test.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);

    cin >> n >> m;
    for (int i = 0; i < m; ++i) {
        cin >> l[i] >> r[i];
        ++num[l[i]];
        --num[r[i] + 1];
    }
    for (int i = 1; i <= n; ++i) {
        tmp += num[i];
        cnt1[i] = cnt1[i - 1];
        if (tmp == 0) {
            ++cnt0;
        } else if (tmp == 1) {
            ++cnt1[i];
        }
    }
    for (int i = 0; i < m; ++i) {
        cout << cnt0 + cnt1[r[i]] - cnt1[l[i] - 1] << endl;
    }

    return 0;
}