CCF-CSP201612-2工资计算，算出倒公式，二十行搞定~

不废话，直接上代码：

#include<iostream>
using namespace std;
int main() {
	int after, pre;
	cin >> after;
	if (after <= 3500)
		cout << after;
	else if (after + 45 <= 5000) 
		cout << 3500 + (after - 3500) / 0.97;
	else if (after + 45 + 300 <= 8000)
		cout << 5000 + (after + 45 - 5000) / 0.9;
	else if (after + 45 + 300 + 900 <= 12500)
		cout << 8000 + (after + 45 + 300 - 8000) / 0.8;
	else if (after + 45 + 300 + 900 + 6500 <= 38500)
		cout << 12500 + (after + 45 + 300 + 900 - 12500) / 0.75;
	else if (after + 45 + 300 + 900 + 6500 + 6000 <= 58500)
		cout << 38500 + (after + 45 + 300 + 900 + 6500 - 38500) / 0.7;
	else if (after + 45 + 300 + 900 + 6500 + 6000 + 8750 <= 83500)
		cout << 58500 + (after + 45 + 300 + 900 + 6500 + 6000 - 58500) / 0.65;
	else if (after + 45 + 300 + 900 + 6500 + 6000 + 8750 > 83500)
		cout << 83500 + (after + 45 + 300 + 900 + 6500 + 6000 + 8750 - 83500) / 0.55;
	return 0;}

思路：
已知个税计算公式，可以自己列个方程，假如收入为x,税后输入为y，5000<x<8000。
y=3500+(x-5000)0.9+15000.97,那么x=(y-4955) / 0.9+5000,以此类推…