洛谷 P5017 摆渡车

题目传送门

解题思路：

个人感觉DP这东西，只可意会，不可言传

AC代码：

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

using namespace std;

long long n,m,t[501],f[501][501],ans = 0x3f3f3f3f3f,mi;

int main() {
    scanf("%lld%lld",&n,&m);
    for(int i = 1;i <= n; i++) 
        scanf("%lld",&t[i]),mi = mi < t[i] ? mi : t[i];    
    for(int i = 1;i <= n; i++) t[i] -= mi;
    sort(t+1,t+n+1);
    memset(f,0x3f,sizeof(f));
    for(int i = 0;i < 2 * m; i++) f[1][i] = i;
    for(int i = 1;i < n; i++)
        for(int j = 0;j < 2 * m; j++) {
            if(f[i][j] < 0x3f3f3f3f3f3f3f3f) {
                if(t[i] + j >= t[i+1])
                    f[i+1][t[i]+j-t[i+1]] = min(f[i+1][t[i]+j-t[i+1]],f[i][j]+j+t[i]-t[i+1]);
                for(int k = t[i] + j + m >= t[i+1] ? 0 : t[i+1] - t[i] - j - m;t[i] + j + m + k - t[i+1] < 2 * m; k++)
                    if(t[i] + j + k + m >= t[i+1])
                        f[i+1][t[i]+j+k+m-t[i+1]] = min(f[i+1][t[i]+j+k+m-t[i+1]],f[i][j]+t[i]+j+m+k-t[i+1]);
                if(t[i] + j + m < t[i+1])
                    for(int k = 0;k < m * 2; k++)
                        f[i+1][k] = min(f[i+1][k],f[i][j] + k); 
            }
        }
    for(int i = 0;i < m * 2; i++)
        ans = min(ans,f[n][i]);
    printf("%lld",ans);
    return 0;
}

//NOIP2018普及 T3