ZOJ 3469 Food Delivery

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long LL;
const LL INF = 1e9+7;
const LL maxn = 1e3+5;
const LL MOD = 1e9+7;
int dp[2][maxn][maxn], sum[maxn];
struct node
{
    int X, B;
    bool friend operator < (node A, node B)
    {
        return A.X < B.X;
    }
} P[maxn];

int main()
{
    int n, v, x;
    while(cin >> n >> v >> x)
    {
        for(int i=1; i<=n; i++)
            cin >> P[i].X >> P[i].B;
        P[n+1].X = x, P[n+1].B = 0;
        n ++;
        memset(dp, 0, sizeof(dp));
        memset(sum, 0, sizeof(sum));
        sort(P+1, P+1+n);

        sum[0] = 0;
        for(int i=1; i<=n; i++)
            sum[i] = sum[i-1] + P[i].B;
        int Star;

        for(int i=0; i<=n+1; i++)
        for(int j=0; j<=n+1; j++)
        dp[0][i][j] = dp[1][i][j] = INF;

        for(int i=1; i<=n; i++)
        {
            if(P[i].X == x)
            {
                Star = i;
                break;
            }
        }
        dp[0][Star][Star] = dp[1][Star][Star] = 0;
        for(int i=Star; i>=1; i--)
        for(int j=Star; j<=n;  j++)
        {
            dp[0][i][j] = min(dp[0][i][j], dp[0][i+1][j] + (P[i+1].X - P[i].X)*(sum[n]-sum[j]+sum[i]) );
            dp[0][i][j] = min(dp[0][i][j], dp[1][i+1][j] + (P[j].X - P[i].X)*(sum[n]-sum[j]+sum[i]) ) ;
            dp[1][i][j] = min(dp[1][i][j], dp[0][i][j-1] + (P[j].X - P[i].X)*(sum[n]-sum[j-1]+sum[i-1]) );
            dp[1][i][j] = min(dp[1][i][j], dp[1][i][j-1] + (P[j].X - P[j-1].X)*(sum[n] - sum[j-1] + sum[i-1]) );
        }
        printf("%d\n", min(dp[0][1][n],dp[1][1][n])*v);
    }
    return 0;
}