CodeForces - 371C (Hamburgers) 做题笔记

发表于 | 更新于 | | 阅读次数：

题目链接：http://codeforces.com/problemset/problem/371/C

这题一开始用的贪心，但WA掉了。
正解是二分一个答案，查看能否用现有的钱买到相应的食材。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
char s[200];
LL ca, cb, cc;
LL na, nb, nc;
LL pa, pb, pc;
LL r;

bool check(LL x) {
	LL need = 0;
	LL cnta = x * ca - na;
	if(ca > 0 && cnta > 0) need += cnta * pa;
	LL cntb = x * cb - nb;
	if(cb > 0 && cntb > 0) need += cntb * pb;
	LL cntc = x * cc - nc;
	if(cc > 0 && cntc > 0) need += cntc * pc;
	if(need > r) return false;
	else return true;
}

int main() {
	scanf("%s%*c", s);
	cin >> na >> nb >> nc;
	cin >> pa >> pb >> pc;
	cin >> r;
	ca = cb = cc = 0LL;
	for(int i = 0; s[i] != '\0'; i++) {
		switch(s[i]) {
			case 'B': ca++;	break;
			case 'S': cb++; break;
			case 'C': cc++; break;
		}
	}
	LL l = 0, r = 1100000000009LL;
	while(l < r) {
		LL mid = (l + r + 1) >> 1;
		if(check(mid)) l = mid;
		else r = mid - 1;
	}
	cout << r;
	return 0;
}