2172 - 计算机C13001第一次小组赛C题
Ms.Han was addicted to games about light .
There are N lights putting in a line S[1...N] and we can change their status (open and closed ) by pressing their button. But they have a characteristic, when you press light s[i] (0<=i<=N), those lights who's numbers are i's multiple will also change their status.For example:There are 10 lights s[1...10] whose initial status is closed. When she press the light s[2] (it will be open), then the light s[2],s[4],s[6],s[8] and s[10] will also be open. When she press s[4] again, light s[4] and s[8] will be closed.Now Ms.Han has N lights all closed ,she will press them from 1 to N ,then how many lights will be open in the end?
题目输入
The input will contain multiple test cases ,Each case will only contain a number N(1 <= N <= 1,000,00).
题目输出
A integer on a single line for each case indicates the number of lights which are open in the end.
输入/输出样例
输入格式
10 15 20
输出格式
3 3 4
C语言解答
#include<stdio.h> void main() { int N,i,count=0; while (scanf("%d",&N)!=EOF) { for(i=1;i<=N;i++) { if(i*i<=N) count+=1; else break; }printf("%d\n",count); count=0; } }
C++解答
#include <iostream> #include <cstdio> #include <cmath> using namespace std; int main() { int a; while(scanf("%d",&a)!=EOF) { int b=sqrt(a); cout<<b<<endl; } return 0; }