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
*/