Submission #427956

#TimeUsernameProblemLanguageResultExecution timeMemory
427956cfalasMonochrome Points (JOI20_monochrome)C++14
35 / 100
167 ms2080 KiB
#include<bits/stdc++.h> using namespace std; #define mp make_pair #define INF 10000000 #define MOD 1000000007 #define MID ((l+r)/2) #define HASHMOD 2305843009213693951 #define ll long long #define ull unsigned long long #define F first #define S second typedef pair<ll, ll> ii; typedef pair<ii, int> iii; typedef vector<int> vi; typedef vector<ii> vii; typedef map<int, int> mii; #define EPS 1e-6 #define FOR(i,n) for(int i=0;i<((int)(n));i++) #define FORi(i,a,b) for(int i=((int)(a));i<((int)(b));i++) #define FOA(v, a) for(auto v : a) int t, n; vi a, b; int dist(int a, int b){ return min(abs(a-b), abs(a-b+n)); } int bp[40000]; int wp[40000]; int br(int l, int r){ if(l>r) return 0; if(l==0) return bp[r]; else return bp[r] - bp[l-1]; } int wr(int l, int r){ if(l>r) return 0; if(l==0) return wp[r]; else return wp[r] - wp[l-1]; } int main(){ cin>>n; string s; cin>>s; n*=2; set<int> w, b; bp[0] = (s[0]=='B'); FORi(i,1,n){ bp[i] = bp[i-1]; if(s[i]=='B') bp[i]++; } wp[0] = (s[0]=='W'); FORi(i,1,n){ wp[i] = wp[i-1]; if(s[i]=='W') wp[i]++; } FOR(i,n){ if(s[i]=='W') w.insert(i); else b.insert(i); } vi c(n); int bans=0; FORi(off,0, n/2+1){ auto it = b.begin(); FOR(i,off) it++; int ans=0; FOA(v,w){ c[v] = *it; c[*it] = v; //cout<<v<<" "<<*it<<endl; // ans = min(b in range + w in other side, w in range + b in other side) int mi = min(v, *it); int ma = max(v, *it); ans += min(br(mi+1,ma-1) , (wr(0,mi-1) + wr(ma+1,n-1))) + min(br(0,mi-1) + br(ma+1,n-1) , (wr(mi+1,ma-1))); //cout<<v<<" "<<*it<<" "<<ans<<endl; it++; if(it==b.end()) it = b.begin(); } //cout<<ans<<endl; /* FOR(i,n){ if(s[i]=='B') FORi(j,min(i,c[i])+1, max(i,c[i])){ if(c[j]>max(i,c[i]) || c[j]<min(i,c[i])) ans++; } }*/ bans = max(bans, ans); } cout<<bans/2<<endl; }
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