单调函数的零点问题(模板）

learn && wrong：

1、f(mid)与2的关系，改成与o的关系
2、f（x）更改一下
3、如果递减，只需要把f(mid)改成小于号

#include <iostream>

const double eps = 1e-5; //精度为10的-5次方（！！！）

double f(double x) {  //计算f(x）
    return ...
}

double calsqrt() {
    double left = 1, right = 2, mid; //[left,right] = [1,2]
    while (right - left > eps) {
        mid = (right - left) / 2;
        if (f(mid) > 0) {
            right = mid;
        }
        else if(f(mid) < 0) {
            left = mid;
        }
    }
    return mid;
}

#include <iostream>

const double eps = 1e-5; //精度为10的-5次方（！！！）

double f(double x) {  //计算f(x）
    return x * x;
}

double calsqrt() {
    double left = 1, right = 2, mid; //[left,right] = [1,2]
    while (right - left > eps) {
        mid = (right - left) / 2;
        if (f(mid) > 2) {
            right = mid;
        }
        else if(f(mid) < 2) {
            left = mid;
        }
    }
    return mid;
}