题目大意
删除最少数,使得数组最大子段和小于 $S$ 。
分析
$S<0$ 显然只统计小于 $S$ 的数的个数。
最大子段和是可以根据 $f_i=\max (f_{i-1},0)+1$ 达到 $\mathcal{O}(n)$ 扫的。尽量避免带修等问题,就考虑一边扫一边微调:当扫到正数时,当前最大子段和是否大于等于 $S$ ,是则删除若干最大值;当扫到负数时,需要若干个最小值与之抵消。
代码
const int N = 1e6 + 5;
inline ll Read() {
ll x = 0, f = 1;
char c = getchar();
while (c != '-' && (c < '0' || c > '9')) c = getchar();
if (c == '-') f = -f, c = getchar();
while (c >= '0' && c <= '9') x = (x << 3) + (x << 1) + c - '0', c = getchar();
return x * f;
}
int n, ans;
ll m, sum;
ll a[N];
multiset<ll> t;
bool vis[N];
int main() {
// freopen("11.in", "r", stdin);
// freopen("1.out", "w", stdout);
n = Read(), m = Read();
for (int i = 1; i <= n; i++) a[i] = Read();
if (m < 0) {
for (int i = 1; i <= n; i++)
if (a[i] >= m) ans++;
printf ("%d\n", ans);
return 0;
}
for (int i = 1; i <= n; i++) {
if (a[i] > 0) {
t.insert(a[i]);
sum += a[i];
while (sum >= m) {
multiset<ll>::iterator mx = t.lower_bound(1ll << 60);
mx--;
sum -= *mx;
ans++;
t.erase(mx);
}
} else {
for (ll val = 0ll; t.size() && val < -a[i]; ) {
multiset<ll>::iterator mn = t.upper_bound(0ll);
sum -= *mn;
val += *mn;
t.erase(mn);
if (val >= -a[i]) {
t.insert(val + a[i]), sum += val + a[i];
break;
}
}
}
}
printf ("%d\n", ans);
return 0;
}