C :

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
char t[1000];
int n;
int tree(int k) {
	if ((t[2*k]=='#'&&t[2*k+1]=='#')||(2*k>n&&(2*k+1>n))) return 1;
		else 	if (2*k<=n&&t[2*k]!='#'&&(2*k+1<=n)&&t[2*k+1]!='#') return tree(2*k)&&tree(2*k+1);
			else return 0;
}

int main(){
	int i;
	scanf("%s",t);
	n=strlen(t);
	for (i=n;i>0;i--) t[i]=t[i-1];
	if (tree(1)) printf("Yes\n");
		else printf("No\n");
	
	return 0;
}

C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<string>
#include<cstdlib>
#include<queue>
#include<vector>
#define INF 0x3f3f3f3f
#define PI acos(-1.0)
#define N 1001
#define MOD 123
#define E 1e-6
using namespace std;
char s[N];
int main()
{
    cin>>s;
    int len=strlen(s);
    s[len]='#';
 
    int flag=true;
    for(int i=1;i<len;i+=2){
        if( (s[i]=='#'&&s[i+1]!='#') || (s[i+1]=='#'&&s[i]!='#') )
        {
            flag=false;
            break;
        }
    }
    if(flag)
        cout<<"Yes"<<endl;
    else
        cout<<"No"<<endl;
    return 0;
}