poj 2393

贪心思想。对于第i周，我们取的价格要么是本周的，要么是前几周生产费用+存储费用。更新下每周的价格以后就可以计算总的最小的花费。

#include<stdio.h>
#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<time.h>
#include<queue>
#include<stack>
#include<iterator>
#include<math.h>
#include<stdlib.h>
#include<limits.h>
#include<map>
#include<set>
#include<bitset>
//#define ONLINE_JUDGE
#define eps 1e-8
#define INF 0x7fffffff
#define FOR(i,a) for((i)=0;i<(a);(i)++)
#define MEM(a) (memset((a),0,sizeof(a)))
#define sfs(a) scanf("%s",a)
#define sf(a) scanf("%d",&a)
#define sfI(a) scanf("%I64d",&a)
#define pf(a) printf("%d\n",a)
#define pfI(a) printf("%I64d\n",a)
#define pfs(a) printf("%s\n",a)
#define sfd(a,b) scanf("%d%d",&a,&b)
#define sft(a,b,num) scanf("%d%d%d",&a,&b,&num)
#define for1(i,a,b) for(int i=(a);i<b;i++)
#define for2(i,a,b) for(int i=(a);i<=b;i++)
#define for3(i,a,b)for(int i=(b);i>=a;i--)
#define MEM1(a) memset(a,0,sizeof(a))
#define MEM2(a) memset(a,-1,sizeof(a))
#define ll __int64
const double PI=acos(-1.0);
template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
template<class T> inline T Min(T a,T b){return a<b?a:b;}
template<class T> inline T Max(T a,T b){return a>b?a:b;}
using namespace std;
//#pragma comment(linker,"/STACK:1024000000,1024000000")
int n,m;
#define M 110
#define N 1000010
#define Mod 258280327
#define p(x,y) make_pair(x,y)
const int MAX_len=550;
int res[50010];
struct Node{
    ll c,y;
}a[10010];
int main(){
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
//  freopen("out.txt", "w", stdout);
#endif
    while(sfd(n,m)!=EOF){
        for(int i=0;i<n;i++)
            scanf("%I64d%I64d",&a[i].c,&a[i].y);
        ll ans=0;
        for(int i=1;i<n;i++) //更新第i周的价格，要么取前几周生产的，要么本周生产.
            a[i].c = Min(a[i-1].c+m,a[i].c);
        for(int i=0;i<n;i++)
            ans += (a[i].c*a[i].y);
        pfI(ans);
    }
    return 0;
}