ZOJ 3469 区间DP Food Delivery

题解

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
#define MP make_pair
using namespace std;

typedef pair<int, int> PII;

const int maxn = 1000 + 10;
const int INF = 0x3f3f3f3f;

PII a[maxn];
int sum[maxn];

int n, v, x;

int d[maxn][maxn][2];

int main()
{
    while(scanf("%d%d%d", &n, &v, &x) == 3)
    {
        for(int i = 1; i <= n; i++) scanf("%d%d", &a[i].first, &a[i].second);
        a[++n] = MP(x, 0);
        sort(a + 1, a + 1 + n);
        for(int i = 1; i <= n; i++) sum[i] = sum[i - 1] + a[i].second;

        int p;
        for(int i = 1; i <= n; i++) if(a[i].first == x) { p = i; break; }
        memset(d, 0x3f, sizeof(d));
        d[p][p][0] = d[p][p][1] = 0;

        for(int i = p; i > 0; i--)
            for(int j = p; j <= n; j++)
            {
                if(i == j) continue;
                int t = sum[i - 1] + sum[n] - sum[j];

                int& ans1 = d[i][j][0];
                ans1 = min(ans1, d[i+1][j][0] + (t + a[i].second) * (a[i+1].first - a[i].first));
                ans1 = min(ans1, d[i+1][j][1] + (t + a[i].second) * (a[j].first - a[i].first));

                int& ans2 = d[i][j][1];
                ans2 = min(ans2, d[i][j-1][0] + (t + a[j].second) * (a[j].first - a[i].first));
                ans2 = min(ans2, d[i][j-1][1] + (t + a[j].second) * (a[j].first - a[j-1].first));
            }

        printf("%d
", min(d[1][n][0], d[1][n][1]) * v);
    }

    return 0;
}