POJ 1860 Currency Exchange (Shortest Path), pojcurrency

POJ 1860 Currency Exchange (Shortest Path), pojcurrency
Currency Exchange

Time Limit:1000 MS		Memory Limit:30000 K
Total Submissions:20482		Accepted:7352

Description

Several currency exchange points are working in our city. let us suppose that each point specializes in two particle currencies and performs exchange operations only with these currencies. there can be several points specializing in the same pair of currencies. each point has its own exchange rates, exchange rate of A to B is the quantity of B you get for 1A. also each exchange point has some commission, the sum you have to pay for your exchange operation. commission is always collected in source currency.
For example, if you want to exchange 100 US Dollars into Russian Rubles at the exchange point, where the exchange rate is 29.75, and the commission is 0.39 you will get (100-0.39) * 29.75 = 2963.20.rur.
You surely know that there are N different currencies you can deal with in our city. let us assign unique integer number from 1 to N to each currency. then each exchange point can be described with 6 numbers: integer A and B-numbers of currencies it exchanges, and real RAB, CAB, RBA and CBA-exchange rates and commissions when exchanging A to B and B to A respectively.
Nick has some money in currency S and wonders if he can somehow, after some exchange operations, increase his capital. of course, he wants to have his money in currency S in the end. help him to answer this difficult question. nick must always have non-negative sum of money while making his operations.

Input

The first line of the input contains four numbers: N-the number of currencies, M-the number of exchange points, s-the number of currency Nick has and V-the quantity of currency units he has. the following M lines contain 6 numbers each-the description of the corresponding exchange point-in specified above order. numbers are separated by one or more spaces. 1 <= S <= N <= 100, 1 <= M <= 100, V is real number, 0 <= V <= 103.
For each point exchange rates and commissions are real, given with at most two digits after the decimal point, 10-2 <= rate <= 102, 0 <= commission <= 102.
Let us call some sequence of the exchange operations simple if no exchange point is used more than once in this sequence. you may assume that ratio of the numeric values of the sums at the end and at the beginning of any simple sequence of the exchange operations will be less than 104.

Output

If Nick can increase his wealth, output YES, in other case output NO to the output file.

Sample Input

3 2 1 20.01 2 1.00 1.00 1.00 1.002 3 1.10 1.00 1.10 1.00

Sample Output

YES

Source

Northeastern Europe 2001, Northern Subregion


There are N currencies, which are exchanged through exchange rates. A person holds a currency and has a certain amount, ask if the amount of money in his hand can be increased through mutual exchange between currencies. If "YES" is added, then "NO" is output ". In addition, the exchange between currencies requires a service fee. For example, if you want to convert $100 into a Russian rubles, the exchange rate is 29.75, and the Commission is 0.39, you will get (100-0.39) * 29.75 = 2963.3975 Russian rubles. Understanding this makes it easy. Data entered in the first row: N currencies, M group data, currency category, amount of currency held, and data entered in the second row to the M + 1 row: x and y are two types of currencies that can be exchanged. The four numbers below represent the exchange rate for converting x into y and the required service fees. And the exchange rate of converting y into x and the required service fees. It can be seen as a short circuit problem: Bellman Ford algorithm code:

#include<stdio.h>#include<string.h>#include<stdlib.h>struct node{    int x,y;    double a,b;} q[1000100];int n,m,s;double k;int t = 0;double num[100010];void add(int x,int y,double a,double b){    q[t].x = x;    q[t].y = y;    q[t].a = a;    q[t++].b = b;}int BF(){    for(int i=1; i<=n; i++)    {        num[i] = 0;    }    num[s] = k;    for(int i=1; i<=n; i++)    {        int flag = 0;        for(int j=0; j<t; j++)        {            if(num[q[j].y]<(num[q[j].x] - q[j].b) * q[j].a)            {                num[q[j].y] = (num[q[j].x] - q[j].b) * q[j].a;                flag = 1;                if((q[j].y == s && num[s]>k) || (q[i].x == s && num[s]>k))                {                    return 1;                }            }        }        if(flag == 0)        {            break;        }    }    for(int j=0; j<t; j++)    {        if(num[q[j].y]<(num[q[j].x] - q[j].b) * q[j].a)        {            num[q[j].y] = (num[q[j].x] - q[j].b) * q[j].a;            return 1;        }    }    return 0;}int main(){    while(scanf("%d%d%d%lf",&n,&m,&s,&k)!=EOF)    {        double a1,b1,a2,b2;        int x1,y1;        t = 0;        for(int i=1; i<=m; i++)        {            scanf("%d%d%lf%lf%lf%lf",&x1,&y1,&a1,&b1,&a2,&b2);            add(x1,y1,a1,b1);            add(y1,x1,a2,b2);        }        int kk = BF();        if(kk == 1)        {            printf("YES\n");        }        else        {            printf("NO\n");        }    }    return 0;}