【Luogu】P1607庙会班车Fair Shuttle（线段树+贪心）

#include <cstdio>
#include <iostream>
#include <algorithm>
#define N 100001
#define min(x, y) ((x) < (y) ? (x) : (y))
#define max(x, y) ((x) > (y) ? (x) : (y))
#define root 1, 1, n
#define ls now << 1, l, mid
#define rs now << 1 | 1, mid + 1, r


int k, n, c, ans;
int sum[N << 2], add[N << 2];

struct node
{
    int s, t, m;
}p[N];

inline int read()
{
    int x = 0, f = 1;
    char ch = getchar();
    for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;
    for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch  - ‘0‘;
    return x * f;
}

inline bool cmp(node x, node y)
{
    return x.t < y.t;
}

inline void pushdown(int now)
{
    if(add[now])
    {
        sum[now << 1] += add[now];
        sum[now << 1 | 1] += add[now];
        add[now << 1] += add[now];
        add[now << 1 | 1] += add[now];
        add[now] = 0;
    }
}

inline int query(int now, int l, int r, int x, int y)
{
    if(x <= l && r <= y) return sum[now];
    pushdown(now);
    int mid = (l + r) >> 1, ret = 0;
    if(x <= mid) ret = max(ret, query(ls, x, y));
    if(mid < y) ret = max(ret, query(rs, x, y));
    return ret;
}

inline void update(int now, int l, int r, int x, int y, int d)
{
    if(x <= l && r <= y)
    {
        sum[now] += d;
        add[now] += d;
        return;
    }
    pushdown(now);
    int mid = (l + r) >> 1;
    if(x <= mid) update(ls, x, y, d);
    if(mid < y) update(rs, x, y, d);
    sum[now] = max(sum[now << 1], sum[now << 1 | 1]);
}

int main()
{
    int i, x;
    k = read();
    n = read();
    c = read();
    for(i = 1; i <= k; i++)
    {
        p[i].s = read();
        p[i].t = read();
        p[i].m = read();
    }
    std::sort(p + 1, p + k + 1, cmp);
    for(i = 1; i <= k; i++)
    {
        x = query(root, p[i].s, p[i].t - 1);
        if(x < c)
        {
            update(root, p[i].s, p[i].t - 1, min(p[i].m, c - x));
            ans += min(p[i].m, c - x);
        }
    }
    printf("%d\n", ans);
    return 0;
}