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用二分法来解方程，但是解同类问题时要注意方程是否有唯一解

#include <iostream>  #include <cstring>#include <cstdio>#include <algorithm>#include <string>#include <string.h>#include <cmath>#include <sstream>#include <set>#include <map>#include <functional>#include <queue>#include <vector>using namespace std;int arr[10010];int n;int main(){    while (scanf("%d", &n) && n != 0)    {        for (int i = 0; i <= n; i++)            scanf("%d", &arr[i]);        arr[0] = -arr[0];        double l = -1.0, r = 1e6, m;        for (int i = 0; i < 100; i++)        {            m = l + (r - l) / 2;            double f = 1.0, s = 0.0;            for (int j = 1; j <= n; j++)            {                f /= (1 + m);                s += f*arr[j];            }            if (s <arr[0])//这里要注意                r = m;            else                l = m;        }        printf("%.2lf\n", m);    }}

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