bool dfs()
{
if(step+score>bound)
{
if(step+score<next)
next=step+score;
return false;
}
if(!score)
{
return true;
path[step]=0;
}
for(int i=0;i<4;i++)
if(path[step-1]!=dirt[rev[i]] && vaild(x+dx[i],y+dy[i]))
{
score-=num[s[x][y]][x][y];
s[x+dx[i]][y+dy[i]]=s[x][y];
s[x+=dx[i]][y+=dy[i]]=0;
score+=num[s[x][y]][x][y];
path[step++]=dirt[i];
if(dfs())
return true;
step--;
score-=num[s[x][y]][x][y];
s[x-dx[i]][y-dy[i]]=s[x][y];
s[x-=dx[i]][y-=dy[i]]=0;
score+=num[s[x][y]][x][y];
}
return false;
}
void solveNQueens(const int n, vector<int> & steps, vector<vector<string> > & res)
{
if (steps.size() == n)
{
vector<string> v;
for (int i = 0; i < n; i++)
{
string tmp(n, '.');
tmp[steps[i]] = 'Q';
v.push_back(tmp);
}
res.push_back(v);
return;
}
else
{
int row = steps.size();
for (int i = 0; i < n; i++)
{
//每走一步，都要看下当前step是否vaild
if (vaild(row, i, steps))
{
//对当前row的每个col进行遍历
steps.push_back(i);
solveNQueens(n, steps, res);
steps.pop_back();
}
}
}
}
vector<string> restoreIpAddresses(string s) {
vector<string> res;
int len = s.size();
if(len < 4 && len > 12) return res;
int point = 1;
int cur = 1;
for(int i = 0; i < 5; i++)dot.push_back(0);
while(point < 4){
while(cur < len){
if(vaild(cur,point,len,s)){
dot[point] = cur;
cur ++;
break;
}
else{
if(cur - dot[point-1] > 3){
//point --;
//cur = dot[point] + 1;
break;
}
else cur ++;
}
}
if(dot[point] == 0){
if(point == 1) break;
else{
point --;
cur = dot[point] + 1;
dot[point] = 0;
continue;
}
}
if(point == 3 && dot[point] != 0){
point = 1;
string temp;
for(int i = 0;i < len;){
if(dot[point] == i){
temp += ".";
point ++;
}
else{
temp += s[i];
i++;
}
}
point --;
res.push_back(temp);
cur = dot[point] + 1;
dot[point] = 0;
//point --;
continue;
}
point ++;
}
return res;
}
inline int read(){int ret=0;char c=gc();while(vaild(c))ret=ret*10+c-'0',c=getchar();return ret;}
inline char gc(){char c=getchar();while(!vaild(c))c=getchar();return c;}
