【题解】慈溪中学-8.15-T1

传送门
二分，枚举答案
如果验证是否能给mid个充电器都充电
那当然是给更安全的充电器充电
然后对于每个充电器是否能充电，总是先尽可能插插线板，然后充电
Code：

#include <bits/stdc++.h>
#define maxn 400010
#define LL long long
using namespace std;
int n, m, a[maxn], b[maxn];

inline int read(){
	int s = 0, w = 1;
	char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') w = -1;
	for (; isdigit(c); c = getchar()) s = (s << 1) + (s << 3) + (c ^ 48);
	return s * w;
}

bool cmp(int x, int y){ return x > y; }

bool check(int mid){
	int A = 1, B = 0, k = mid, i = 1, L = 0;
	while (k <= m){
		while (L < b[k] && A && i <= n){
			--A, B += a[i++];
			if (!A) A = B, B = 0, ++L;
		}
		if (!A || L > b[k]) return 0;
		if (L < b[k]) A += B, B = 0;
		--A, ++k;
		if (!A) A = B, B = 0, ++L;
	}
	return k > m;
}

int main(){
	n = read(), m = read();
	for (int i = 1; i <= n; ++i) a[i] = read();
	for (int i = 1; i <= m; ++i) b[i] = read();
	sort(a + 1, a + 1 + n, cmp);
	sort(b + 1, b + 1 + m);
	int l = 1, r = m, ans;
	while (l <= r){
		int mid = (l + r) >> 1;
		if (check(mid)) ans = max(ans, m - mid + 1), r = mid - 1; else l = mid + 1;
	}
	printf("%d\n", ans);
	return 0;
}