1 #include<stdio.h>
 2 #include<string.h>
 3 #define MIN(x,y)(x<y?x:y)
 4 int len,flot,ans;
 5 int s[25];
 6 void turn(int x){
 7     s[x]=!s[x];
 8     if(x-1>=0)s[x-1]=!s[x-1];
 9     if(x+1<len)s[x+1]=!s[x+1];
10 }
11 bool find(){
12     for(int i=0;i<len;i++){
13     //    printf("%d ",s[i]);
14         //if(s[i])puts("");
15         if(s[i])return false;
16     }
17     return true;
18 }
19 void dfs(int x,int time){
20     if(find()){
21         flot=1;
22         ans=MIN(ans,time);
23         return;
24     }
25     if(x>=len)return;
26     dfs(x+1,time);
27     turn(x);
28     dfs(x+1,time+1);
29     turn(x);
30 }
31 int main(){
32     char m[20];
33     while(~scanf("%s",m)){
34         len=strlen(m);
35         for(int i=0;i<len;i++)s[i]=m[i]-‘0‘;
36         s[len]=‘\0‘;
37         ans=0x3f3f3f3f;
38         flot=0;
39         dfs(0,0);
40         //printf("%d\n",ans);
41         if(flot)printf("%d\n",ans);
42         else puts("NO");
43     }
44     return 0;
45 }

 1 #include<stdio.h>
 2 #include<string.h>
 3 #define MIN(x,y)(x<y?x:y)
 4 int len,flot,ans;
 5 int s[25],cnt[25];
 6 void turn(int x){
 7     s[x]=!s[x];
 8     if(x-1>=0)s[x-1]=!s[x-1];
 9     if(x+1<len)s[x+1]=!s[x+1];
10 }
11 bool find(){
12     for(int i=0;i<len;i++){
13     //    printf("%d ",s[i]);
14         //if(s[i])puts("");
15         if(s[i])return false;
16     }
17     return true;
18 }
19 void dfs(int x){
20     if(find()){
21         flot=1;
22         int temp=0;
23         for(int i=0;i<len;i++)if(cnt[i]==1)temp++;
24         ans=MIN(ans,temp);
25         return;
26     }
27     if(x>=len)return;
28     for(cnt[x]=0;cnt[x]<2;){
29     turn(x);
30     cnt[x]++;
31     dfs(x+1);
32     }
33 }
34 int main(){
35     char m[20];
36     while(~scanf("%s",m)){
37         len=strlen(m);
38         for(int i=0;i<len;i++)s[i]=m[i]-‘0‘;
39         s[len]=‘\0‘;
40         ans=0x3f3f3f3f;
41         flot=0;
42         memset(cnt,0,sizeof(cnt));
43         dfs(0);
44         //printf("%d\n",ans);
45         if(flot)printf("%d\n",ans);
46         else puts("NO");
47     }
48     return 0;
49 }