51Nod-1636-教育改革

描述

题解

代码

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

typedef long long ll;

const int MAXN = 55;
const int MAXM = 105;

int N, M, K;

struct lesson
{
ll a, b, c;

bool operator < (const lesson &t) const
{
return c < t.c;
}
} les[MAXN];

ll ans = -1;
ll dp[MAXN][MAXN][MAXM];

void _max(ll &a, ll b)
{
a = max(a, b);
}

int main()
{
cin >> N >> M >> K;

for (int i = 1; i <= M; ++i)
{
scanf("%lld%lld%lld", &les[i].a, &les[i].b, &les[i].c);
}

memset(dp, -1, sizeof dp);

sort(les + 1, les + M + 1);

for (int i = 1; i <= M; ++i)
{
for (ll j = les[i].a; j <= les[i].b; ++j)
{
_max(dp[i][1][j - les[i].a], j);
for (int k = M; les[i].c < les[k].c; --k)
{
if (les[k].a <= j + K && j + K <= les[k].b)
{
for (int l = min(i, N - 1); l; --l)
{
if (dp[i][l][j - les[i].a] > 0)
{
_max(dp[k][l + 1][j + K - les[k].a], dp[i][l][j - les[i].a] + j + K);
}
}
}
if (les[k].a <= j * K && j * K <= les[k].b)
{
for (int l = min(i, N - 1); l; --l)
{
if (dp[i][l][j - les[i].a] > 0)
{
_max(dp[k][l + 1][j * K - les[k].a], dp[i][l][j - les[i].a] + j * K);
}
}
}
}
}
}

for (int i = 1; i <= M; ++i)
{
for (ll j = les[i].b - les[i].a; ~j; --j)
{
_max(ans, dp[i]
[j]);
}
}

if (ans == -1)
{
puts("NO");
}
else
{
printf("YES\n%lld\n", ans);
}

return 0;
}