[USACO11DEC]Umbrellas for Cows
我dp真是太弱了，这么简单dp都不会。
令dp[i]表示前 i 头牛头被遮住了的最低成本。则dp[i] = min{dp[i], dp[j - 1] + c[a[i] - a[j] + 1]} (1 <= j <= i)
然后别忘了预处理后缀最小值。
1 #include<cstdio> 2 #include<iostream> 3 #include<cmath> 4 #include<algorithm> 5 #include<cstring> 6 #include<cstdlib> 7 #include<cctype> 8 #include<vector> 9 #include<stack> 10 #include<queue> 11 using namespace std; 12 #define enter puts("") 13 #define space putchar(' ') 14 #define Mem(a, x) memset(a, x, sizeof(a)) 15 #define rg register 16 typedef long long ll; 17 typedef double db; 18 const ll INF = 1e12; 19 const db eps = 1e-8; 20 const int maxn = 5e3 + 5; 21 const int maxm = 1e5 + 5; 22 inline ll read() 23 { 24 ll ans = 0; 25 char ch = getchar(), last = ' '; 26 while(!isdigit(ch)) last = ch, ch = getchar(); 27 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar(); 28 if(last == '-') ans = -ans; 29 return ans; 30 } 31 inline void write(ll x) 32 { 33 if(x < 0) x = -x, putchar('-'); 34 if(x >= 10) write(x / 10); 35 putchar(x % 10 + '0'); 36 } 37 38 int n, m, a[maxn], c[maxm]; 39 ll dp[maxn]; 40 41 int main() 42 { 43 n = read(); m = read(); 44 for(int i = 1; i <= n; ++i) a[i] = read(); 45 sort(a + 1, a + n + 1); 46 for(int i = 1; i <= m; ++i) c[i] = read(); 47 for(int i = m - 1; i; --i) c[i] = min(c[i], c[i + 1]); 48 for(int i = 1; i <= n; ++i) dp[i] = INF; 49 for(int i = 1; i <= n; ++i) 50 for(int j = 1; j <= i; ++j) 51 dp[i] = min(dp[i], dp[j - 1] + c[a[i] - a[j] + 1]); 52 write(dp[n]), enter; 53 return 0; 54 }
