This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
using namespace std;
#define INF 1e6
int main(){
int n; cin>>n;
vector<int> a(n+1);
for(int i = 1; i <= n; i++){
char c; cin>>c;
a[i] = c - 'a';
}
vector<vector<int> > next(n+2, vector<int>(10, INF));
for(int i = n; i > 0; i--){
next[i] = next[i+1];
next[i][a[i]] = i;
}
vector<vector<int> > pref(n+2, vector<int>(10, 0));
for(int i = 1; i <= n; i++){
pref[i] = pref[i-1];
pref[i][a[i]]++;
}
vector<vector<int> > dp(n+2, vector<int>(10, INF));
for(int i = 0; i < 10; i++){
dp[n+1][i] = 0;
}
for(int i = n; i > 0; i--){
for(int j = 0; j < 10; j++){
int cur = next[i][j]; //cursor is here. need to delete all from i to n
if(cur == INF) continue;
//first come back to the leftest e
if(j == 4){
continue;
}
int indx = next[i][4];
if(indx == INF){ //no e's after i
dp[i][j] = 0;
}else if(indx > cur){
//this section has no e's so just move forward by exactly one fk
for(int k = 0; k < 10; k++){
if(k == 4) continue;
dp[i][j] = min(dp[i][j], 2 + dp[cur+1][k]); //cursor moves to next[cur+1][k]
}
}else if(next[cur+1][4] == INF){
int cost = cur - indx + pref[cur][4] - pref[indx-1][4];
dp[i][j] = cost;
}else{
//first go left to reach leftest e.
int cost = cur - indx + pref[cur][4] - pref[indx-1][4];
//jump from indx+1 to next[cur+1][k]
//find next element, after
int after = cur;
for(int k = 0; k < 10; k++){
if(k == 4) continue;
after = min(after, next[indx][k]);
}
int oc = INF;
for(int k = 0; k < 10; k++){
if(k == 4) continue;
if(next[cur+1][k] == INF) continue;
oc = min(oc, dp[cur+1][k] + 2*(pref[next[cur+1][k]][k] - pref[after][k]));
}
dp[i][j] = min((int)INF, oc + cost);
}
}
// cout<<"DP "<<i<<" : ";
// for(int j = 0; j < 10; j++){
// cout<<dp[i][j]<<"\t";
// }
// cout<<endl;
}
int ans = dp[1][a[1]];
// for(int i = 0; i < 10; i++){
// ans = min(ans, dp[1][i]);
// }
cout<<ans<<endl;
}
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