Food Delivery ZOJ - 3469（区间dp）

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#include<stack>
#include<cstdio>
#include<map>
#include<set>
#include<string>
#include<queue>
using namespace std;
#define inf 0x3f3f3f3f
#define ri register int
typedef long long ll;

inline ll gcd(ll i,ll j){
	return j==0?i:gcd(j,i%j);
}
inline ll lcm(ll i,ll j){
	return i/gcd(i,j)*j;
}
inline void output(int x){
	if(x==0){putchar(48);return;}
	int len=0,dg[20];
	while(x>0){dg[++len]=x%10;x/=10;}
	for(int i=len;i>=1;i--)putchar(dg[i]+48);
}
inline void read(int &x){
    char ch=x=0;
    int f=1;
    while(!isdigit(ch)){
    	ch=getchar();
		if(ch==‘-‘){
			f=-1;
		}	
	}
    while(isdigit(ch))
        x=x*10+ch-‘0‘,ch=getchar();
        x=x*f;
}
const int maxn=1e3+5;
struct st{
	int x,w;
	bool operator < (const st tem)const{
		return x<tem.x;
	}
}stm[maxn];
int sum[maxn];
int dp[maxn][maxn][2];
int n,v,x;
int count(int l,int r){
	if(l<=r)
	return sum[r]-sum[l-1];
	return 0;
}
void solve(){
	memset(dp,0x3f,sizeof(dp));
	int res;
	for(int i=1;i<=n+1;i++){
		if(stm[i].x==x){
			res=i;//找到起点 
			break;
		}
	}
	dp[res][res][0]=dp[res][res][1]=0;
	for(int i=res;i>=1;i--){
		for(int j=res;j<=n+1;j++){
			int tem=count(1,i-1)+count(j+1,n+1);
			if(i==j)
			continue;
			dp[i][j][0]=min(dp[i][j][0],dp[i+1][j][0]+(stm[i+1].x-stm[i].x)*(tem+stm[i].w));
			dp[i][j][0]=min(dp[i][j][0],dp[i+1][j][1]+(stm[j].x-stm[i].x)*(tem+stm[i].w));
			dp[i][j][1]=min(dp[i][j][1],dp[i][j-1][0]+(stm[j].x-stm[i].x)*(tem+stm[j].w));
			dp[i][j][1]=min(dp[i][j][1],dp[i][j-1][1]+(stm[j].x-stm[j-1].x)*(tem+stm[j].w));
		}
	}
	return ;
}
int main(){
	while(scanf("%d%d%d",&n,&v,&x)!=EOF){
		memset(sum,0,sizeof(sum));
		for(int i=1;i<=n;i++){
			scanf("%d%d",&stm[i].x,&stm[i].w);
		}
		stm[n+1].x=x;
		stm[n+1].w=0;
		sort(stm+1,stm+n+2);
		for(int i=1;i<=n+1;i++){
			sum[i]=sum[i-1]+stm[i].w; 
		}
		solve();
		printf("%d\n",min(dp[1][n+1][0],dp[1][n+1][1])*v);
	}
	return 0;
}