Submission #15611001

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Source Code Expand

#include <bits/stdc++.h>
#define x first
#define y second
#define int int long long // 2e9 & 9e18
using namespace std; const int inf = numeric_limits<int>::max();
struct __io{__io(){ios_base::Init i; ios_base::sync_with_stdio(0); cin.tie(0);}} __io; // fast I/O
#ifdef LOCAL // setting up print debugging (yes lol)
template<class K, class V>ostream& operator<<(ostream&s,const pair<K,V>&p){s<<'<'<<p.x<<", "<<p.y<<'>';return s;}
template<class T, class=typename T::value_type, class=typename enable_if<!is_same<T,string>::value>::type>
ostream& operator<<(ostream&s,const T&v){s<<'[';for(auto&x:v){s<<x<<", ";}if(!v.empty()){s<<"\b\b";}s<<']';return s;}
void __prnt(){cerr<<endl;} template<class T, class...Ts>void __prnt(T&&a,Ts&&...etc){cerr<<a<<' ';__prnt(etc...);}
#define print(...) __prnt(__VA_ARGS__)
#else
#define print(...)
#endif

signed main() {
    int n;
    cin >> n;
    string s;
    cin >> s;
    int i = 0;
    int j = n - 1;
    int cnt = 0;
    while (i < n && j >= 0 && i < j) {
    	while (i < n && s[i] == 'R') {
    		++i;
    	}
    	while (j >= 0 && s[j] == 'W') {
    		--j;
    	}
    	if (i < n && j >= 0 && i < j) {
    		swap(s[i], s[j]);
    		cnt++;
    	}
    }
    cout << cnt << endl;
}

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