Energy Conversion
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 7140 Accepted Submission(s): 1715
/***********************************
*
* acm: 2014百度之星資格賽-1001
*
* title: Energy Conversion
*
* time : 2014.5.7
*
***********************************/
#include <stdio.h>
#include <stdlib.h>
#define ll __int64
int main()
{
int T;
int i = 0;
scanf("%d", &T);
while (i < T)
{
ll N; //需要的能量值,開啓大門
ll M; //現在本身擁有的能量值
ll V; //轉換能量的需要耗費的基值
ll K, A; //(A - V)*K //A表示當前能量值,K是擴大的倍數
ll n = 0; //幾次才能轉換完畢
int flag = -1;//判斷是否能轉換(即是否有解)
scanf("%I64d%I64d%I64d%I64d", &N, &M, &V, &K);
A = M;
if (A >= N)
{
flag = 0;
}
else if ((A-V)*K <= A) //隱含A<N
{
flag = -1;
}
else //A < N and 有解 (A-V)*K > A
{
flag = 0;
while (A < N)
{
A = (A-V)*K;
n++;
}
}
if (flag == -1)
{
printf("%d\n", flag);
}
else
{
printf("%I64d\n", n);
}
i++;
}
return 0;
}