There is a problem with the light switch from 1 to 100

Yes 1 To 100 No. 1 light , All lit up at first . Each light has a separate switch , And the switch has only “ open ” and “ Turn off ” Two kinds of state .
Put all... For the first time 1 Press the switch of multiple lamp once , The second time, put all 2 Press the switch of the multiple lamp , Until the hundredth time 100 Press the switch of the multiple lamp .
ask , How many lights are still off ？

One 、Java Programming to solve

package test;

import java.util.ArrayList;
import java.util.List;

public class lamp1_100 {
	public static void main(String[] args){
		int count=0;
		List<Integer> dd = new ArrayList<Integer>();
//	 All lights are on by default 
		for(int i=0;i<100;i++){
			dd.add(1);
		}
//		 Operate all lights 
		for(int k=1;k<=100;k++){
			// Yes k If the operation is set to the on multiple   If it is on, set it to off 
			for(int t=1;t<=100/k;t++){
				if(dd.get((k*t)-1)==0){
					dd.set((k*t)-1,1);
				}else{
					dd.set((k*t)-1,0);
				}
			}
		}
//	 Count the number of lights that are off 
		for(int i=0;i<100;i++){
			if(dd.get(i)==0){
				count++;
				System.out.println(" The remaining index lights are off ："+ i);
			}
		}
		System.out.println(" Number of lights remaining off ："+count);
	}

}

Two 、python The dictionary solves

 The bulb has two states ： On and off , use  -1 On behalf of Guan , use 1 On behalf of . After each operation , Multiply the state by -1.
on ---> 1     off ---> -1

dic = {k:1 for k in range(1,101)}

def lanm(n):
    for i in range(1,n+1):

        for x in dic:
            if x%i == 0:
                dic[x] = int(dic[x])*-1

    return dic


num = len({k: v for k,v in lanm(100).items() if v == 1})
print(f"There are {num} lights on.")

#There are 10 lights on.

3、 ... and 、python list

lamp = []
# Default 100 All the lights are on 
for i in range(100):
    lamp.append(1)
# loop 100 Lights 
for k in range(1,101):
    i = 0
# Yes k Multiple of the lamp for switching operation 
    while i <= 100/k:
        if lamp[(i*k)-1] == 0:
            lamp[(i * k) - 1] = 1
        else:
            lamp[(i*k)-1]=0
        i += 1
#count = len([i for i in lamp if i==0])
count = 0
for i in range(0,100):
    if lamp[i] == 0:
        count +=1
        print(f" Where the lights are off {i+1}")
print(f" Number of lights off {count}")