牛客寒假训练营2-H施魔法

思路

　　dp去维护前缀f[i-1] - ai的最小值

　　

 CODE

#include <bits/stdc++.h>
#define dbg(x) cout << #x << "=" << x << endl

using namespace std;
typedef long long LL;

template<class T>inline void read(T &res)
{
    char c;T flag=1;
    while((c=getchar())<'0'||c>'9')if(c=='-')flag=-1;res=c-'0';
    while((c=getchar())>='0'&&c<='9')res=res*10+c-'0';res*=flag;
}

namespace _buff {
    const size_t BUFF = 1 << 19;
    char ibuf[BUFF], *ib = ibuf, *ie = ibuf;
    char getc() {
        if (ib == ie) {
            ib = ibuf;
            ie = ibuf + fread(ibuf, 1, BUFF, stdin);
        }
        return ib == ie ? -1 : *ib++;
    }
}

int qread() {
    using namespace _buff;
    int ret = 0;
    bool pos = true;
    char c = getc();
    for (; (c < '0' || c > '9') && c != '-'; c = getc()) {
        assert(~c);
    }
    if (c == '-') {
        pos = false;
        c = getc();
    }
    for (; c >= '0' && c <= '9'; c = getc()) {
        ret = (ret << 3) + (ret << 1) + (c ^ 48);
    }
    return pos ? ret : -ret;
}

const int kmaxn = 1007;
LL f[kmaxn];
LL a[kmaxn];
int n,k;

int main()
{
    read(n);
    read(k);
    for(int i = 1; i <= n; ++i) {
        read(a[i]);
    }

    sort(a+1, a+n+1);
    LL temp = -a[1];
    for(int i = 1; i < k; ++i) {
        f[i] = 1 << 30;
    }
    for(int i = k; i <= n; ++i) {
        f[i] = temp + a[i];
        printf("f[%d]:%lld
",i,f[i]);
        temp = min(temp, f[i-k+1] - a[i-k+2]);
        dbg(temp);
        printf("f[%d]:%lld
",i,f[i]);
    }
    printf("%lld
",f[n]);
    return 0;
}