BZOJ5068: 友好的生物(状压 贪心)

题意

题目链接

Sol

又是一道神仙题？？。。

把绝对值拆开之后状压前面的符号？。。

下界显然，但是上界为啥是对的呀qwq。。

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
inline int read() {
    char c = getchar(); int x = 0, f = 1; 
    while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int N, K, C[MAXN], ans;
struct Node {
	int v[6], vk;
	bool operator < (const Node &rhs) const {
		return vk < rhs.vk;
	}
}a[MAXN];
int main() {
	N = read(); K = read() - 1;
	for(int i = 0; i <= K; i++) C[i] = read();
	for(int i = 1; i <= N; i++) {
		for(int j = 0; j < K; j++) a[i].v[j] = read() * C[j]; a[i].vk = read() * C[K];
	}
	sort(a + 1, a + N + 1);
	for(int sta = 0; sta < (1 << K); sta++) {
		int mn = 1e9 + 10;
		for(int i = 1; i <= N; i++) {
			int now = 0;
			for(int j = 0; j < K; j++) 
				now += (sta >> j & 1) ? -a[i].v[j] : a[i].v[j];
			now -= a[i].vk;
			ans = max(ans, now - mn);
			mn = min(now, mn);
		}
	}
	cout << ans;
	return 0;
}
/*
5 3
1 2 3
-5 3 2
-2 3 0
0 5 9
3 4 -1
-10 -11 7
*/