面试OR笔试10——小数转字符串

1 题目及要求

1.1 题目描述

输入一个小数x，输出保留n位小数的近似值(四舍五入)的字符串。如果末尾有0则删除。

如：x = 3.120051, 当n=3时输出3.12,n = 4时输出3.1201

 

2 解答

2.1 代码

string dtos_m(double x, int n =0){string res;if(x<0) {res.push_back('-');x = -x;}int xint = (int) x, base(10);x -= xint;if(!xint) res.push_back('0');else{while(base <= xint) base*=10;for( int bk(base/10);bk;bk/=10){res.push_back('0'+xint/bk);xint = xint % bk;}}base = 1;n = n < 0 ? 0 : n;for (int k1(0); k1 < n; ++k1) {x *= 10;base *= 10;}x+=0.5;xint = (int) x;if(!xint) return res;res.push_back('.');for( int bk(base/10);xint;bk/=10){res.push_back('0'+xint/bk);xint = xint % bk;}return res;}