正整数求n不用sqrt
2020-03-20 12:08 legend聪 阅读(193) 评论(0) 编辑 收藏 举报二分法求根,四舍五入可以用round函数,正整数要用double来取。
#include <stdio.h> #include <stdlib.h> #include <math.h> #include<iostream> using namespace std; #define ACCURACY 0.001 double newSqrt(double n) { double low, high, mid, tmp; // 获取上下界 if (n > 1) { low = 1; high = n; } else { low = n; high = 1; } // 二分法求开方 while (low <= high) { mid = (low + high) / 2.000; tmp = mid * mid; if (tmp - n <= ACCURACY && tmp - n >= ACCURACY * -1) { return mid; } else if (tmp > n) { high = mid; } else { low = mid; } } return -1.000; } int main(void) { double n, res; cin >> n; res = newSqrt(n); printf("%lf\n", res); return 0; }
还可以用牛顿迭代法
#include<cstdio> #include<iostream> using namespace std; #define accuracy 0.01 int main() { double n; cin >> n; double x1; x1 = 1; while (abs(x1*x1 - n)>accuracy) { x1= (x1 + n / x1) / 2.00; } cout << round(x1); }