hdu_4823_Energy Conversion

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=4823

题意：中文题，很清楚，要注意的是乘起来会爆int

题解：

#include<cstdio>int main(){long long t,n,m,v,k,ans,pre;scanf("%d",&t);while(t--){scanf("%I64d%I64d%I64d%I64d",&n,&m,&v,&k);if(m>=n)printf("0\n");else{ans=0,pre=-1;while(m<n&&m>=v&&pre!=m){pre=m,m=(m-v)*k,ans++;}if(m>=n)printf("%I64d\n",ans);else printf("-1\n");}}return 0;}