家人们谁懂啊

我再也不学竞赛了

这是我此生第一道题，听大佬们说最简单的是线段树

可是我写了这么多，才10分，我已经哭晕在厕所

#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define mem(i,a) memset(i,a,sizeof(i))
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
#define pii pair <ll, ll>
const ll INF = 1e18;
const ll DMAX = 1000000+15;
const ll MOD = 1000000007;
const ll G = 3;
const ll invG = 332748118;
ll ans;

ll n, m;

ll a[DMAX];
int q;
struct SegTree{
    ll tag, sum;
    int l, r;
    SegTree (){
        tag = sum = 0;
    }
};
SegTree tr[DMAX];
void pushup (int p) {
    tr[p].sum = tr[p << 1].sum + tr[p << 1 | 1].sum;
}
void build(int p, int l, int r) {
    tr[p].l = l, tr[p].r = r;
    if(l == r){
        tr[p].sum = a[l];
        return ;
    }
    int mid = (l + r) >> 1;
    build (p << 1, l, mid);
    build (p << 1 | 1, mid + 1, r);
    pushup (p);
}

template <class T> inline void read (T &x) {
    x=0;
    T f = 1;
    char ch = getchar ();
    while (ch < '0' || ch > '9') {
        if(ch == '-'){
            f = -1;
        }
        ch = getchar ();
    }
    while (ch <= '9' && ch >= '0') {
        x = x * 10 + (ch - '0');
        ch = getchar ();
    }
    x *= f;
}

template <class T> void write (T x) {
    if(x < 0) {
        putchar ('-');
        x = -x;
    }
    int a[20];
    int cnt = 0;
    do {
        a[++ cnt] = x % 10;
        x /= 10;
    } while (x > 0);
    for(int i = cnt; i >= 1; i --) {
        putchar (a[i] + '0');
    }
    puts ("");
}

void spread (int p) {
    if (tr[p].tag) {
        tr[p << 1].tag += tr[p].tag, tr[p << 1 | 1].tag += tr[p].tag;
        tr[p << 1].sum += (tr[p << 1].r - tr[p << 1].l + 1) * tr[p].tag;
        tr[p << 1 | 1].sum += (tr[p << 1 | 1].r - tr[p << 1|1].l + 1) * tr[p].tag;
        tr[p].tag = 0;
    }
}

void add (int p, int l, int r, ll val) {
    if(l <= tr[p].l && tr[p].r <= r) {
        tr[p].sum += ll (tr[p].r - tr[p].l + 1) + val;
        ++ ans;
        tr[p].tag += val;
        return ;
    }
    spread (p);
    int mid = (tr[p].l + tr[p].r) >> 1;
    if(l <= mid) {
        add (p << 1, l, r, val);
    }
    if(r > mid) {
        add (p << 1 | 1, l, r, val);
    }
    pushup (p);
}

signed main () {
    
    read(n);
    read(m);
    
    build(1, 1, m);
    
    
    for (int i = n; i <= m; i ++) {
		add (1, i, i, 1);
	}
	ans += n;
	write (ans);
    
    return 0;
}

记录