CodeForces-816B Karen and Coffee

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CodeForces-816B Karen and Coffee

题意: 给定一些区间和查询以及一个数k, 查询[l, r]区间内出现了大于等于k次的区间长度的总和.
分析: 预处理区间, 给定区间的首和尾记录下来, 在判断是否大于等于k, 进行累加即可, 详情见代码.
代码:

#include <iostream>
#include <cstring>
using namespace std;

const int MAXN = 2e5 + 10;
int a[MAXN], b[MAXN];
int main()
{
    int n, k, q;
    memset(a, 0, sizeof(a));
    memset(b, 0, sizeof(b));
    cin >> n >> k >> q;
    for (int i = 0; i < n; i++)
    {
        int l, r;
        cin >> l >> r;
        a[l]++, a[r + 1]--;
    }

    int t = 0;

    for (int i = 1; i < MAXN; i++)
    {
        t += a[i];
        if (t >= k)
            b[i] = b[i - 1] + 1;
        else
            b[i] = b[i - 1];
    }

    for (int i = 0; i < q; i++)
    {
        int l, r;
        cin >> l >> r;
        cout << b[r] - b[l - 1] << endl;
    }
}