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2 years ago
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
int n; //n:表示贷款的原值
int m; //m:表示每月支付的分期付款金额
int K; //k:分期付款还清贷款所需的总月数
const double eps = 1e-8; // eps表示精度取决于题目对精度的要求
/**
for()kk
x
1 n+n*x m n+n*x-m
2 (n+n*x-m)+(n+n*x-m)*x m
...
k
> 0 x mmid
*/
bool check(double mid) {
double t = n; //贷款额
for (int i = 1; i <= k; ++i) {//k个月
t += t * mid; //贷款的利息在增加
t -= m; //货款的金额在减少
}
return t > 0; //还了足够的金额
}
int main() {
cin >> n >> m >> k;
double l = 0, r = 5;
while (r - l > eps) {
double mid = (l + r) / 2;
if (check(mid)) r = mid; // 如果还欠银行钱,说明利率太高,需要调低
else l = mid; //如果不欠银行钱,说明利率太低,需要调高
}
printf("%.1f", l * 100);//因为要显示百分比所以乘100
return 0;
}