chore: solved hard day 6 task

hard/day_6/solution.cpp

@@ -1 +1,92 @@
 //Write your code here
+// luogu-judger-enable-o2
+#include<bits/stdc++.h>
+using namespace std;
+#define fo(i,a,b) for(int i=a;i<=b;i++)
+char l[1010],r[1010];
+int ct,c[20000][10],fa[20000],s[17000][2010],n,f[2005][17000],ok[2005][17000],l1,l2;
+int nt(int x,int y){
+	return !c[x][y]?c[x][y]=++ct:c[x][y];
+}
+void ins(){
+	l1=strlen(l+1),l2=strlen(r+1);
+	int x=0,y=0;
+	if(l1==l2){
+		fo(i,1,l1){
+			if(x==y){
+				fo(j,l[i]-'0'+1,r[i]-'0'-1)
+	                s[nt(x,j)][l1-i]++;
+                x=nt(x,l[i]-'0');
+                y=nt(y,r[i]-'0');
+			}
+			else{
+				fo(j,l[i]-'0'+1,9)
+		            s[nt(x,j)][l1-i]++;
+                x=nt(x,l[i]-'0');
+                fo(j,(i==1),r[i]-'0'-1)
+                	s[nt(y,j)][l2-i]++;
+                y=nt(y,r[i]-'0');
+			}
+		}
+		s[x][0]++;
+		if(x!=y)s[y][0]++;
+	}
+	else{
+		fo(i,1,l1){
+			fo(j,l[i]-'0'+1,9)
+				s[nt(x,j)][l1-i]++;
+			x=nt(x,l[i]-'0');
+		}
+		fo(i,1,l2){
+			fo(j,(i==1),r[i]-'0'-1)
+				s[nt(y,j)][l2-i]++;
+			y=nt(y,r[i]-'0');
+		}
+		fo(i,l1+1,l2-1)fo(j,1,9)
+			s[nt(0,j)][i-1]++;
+		s[x][0]++;
+		s[y][0]++;
+	}
+}
+queue<int>q;
+void bd(){
+    fo(i,0,9)if(c[0][i])
+	    q.push(c[0][i]);
+    while(!q.empty()){
+    	int x=q.front();
+    	q.pop();
+    	fo(i,0,l2-1)s[x][i]+=s[fa[x]][i];
+        fo(i,0,9){
+        	if(c[x][i]){
+        		q.push(c[x][i]);
+        		fa[c[x][i]]=c[fa[x]][i];
+			}
+			else c[x][i]=c[fa[x]][i];
+		}
+	}
+	fo(i,0,ct)fo(j,1,n)
+        s[i][j]+=s[i][j-1];
+}
+int main(){
+	scanf("%s%s%d",l+1,r+1,&n);
+	ins();
+	bd();
+	memset(f,-32,sizeof(f));
+	f[0][0]=0;
+	fo(i,0,n-1)fo(j,0,ct)if(f[i][j]>=0)
+		fo(k,0,9)f[i+1][c[j][k]]=max(f[i+1][c[j][k]],f[i][j]+s[c[j][k]][n-i-1]);
+	int r=-1e9;
+	fo(i,0,ct)r=max(r,f[n][i]);
+	printf("%d\n",r);
+	fo(i,0,ct)ok[n][i]=(r==f[n][i]);
+	for(int i=n-1;i;i--)
+		fo(j,0,ct)fo(k,0,9)
+			ok[i][j]|=ok[i+1][c[j][k]]&&(f[i+1][c[j][k]]==f[i][j]+s[c[j][k]][n-i-1]);
+	int x=0;
+	fo(i,1,n)fo(k,0,9)
+		if(ok[i][c[x][k]]&&f[i][c[x][k]]==f[i-1][x]+s[c[x][k]][n-i]){
+			printf("%d",k);
+			x=c[x][k];
+			break;
+		}
+}