Codeforces 1107F Vasya and Endless Credits dp（看题解）

Vasya and Endless Credits

感觉是很巧妙的dp啊， 想到了分成两种信用卡， 并且有一种需要按b排序， 但是没想出怎么dp。。

#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);

using namespace std;

const int N = 500 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double PI = acos(-1);

template<class T, class S> inline void add(T& a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T& a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T& a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T& a, S b) {return a > b ? a = b, true : false;}

int n;
LL dp[N][N];

struct Node {
    int a, b, k;
    void read() {
        scanf("%d%d%d", &a, &b, &k);
    }
    bool operator < (const Node &rhs) const {
        return b > rhs.b;
    }
} offers[N];

int main() {
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) offers[i].read();
    sort(offers + 1, offers + 1 + n);
    LL ans = 0;
    memset(dp, 0xc0, sizeof(dp));
    dp[0][0] = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = 0; j <= i; j++) {
            chkmax(dp[i][j], dp[i - 1][j]);
            chkmax(dp[i][j], dp[i - 1][j] + offers[i].a - 1LL * offers[i].k * offers[i].b);
            if(j) chkmax(dp[i][j], dp[i - 1][j - 1] + offers[i].a - 1LL * (j - 1) * offers[i].b);
            chkmax(ans, dp[i][j]);
        }
    }
    printf("%lld\n", ans);
    return 0;
}

/*
*/