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  1. // ~~ icebear love attttttt ~~
  2. #include <bits/stdc++.h>
  3. using namespace std;
  4.  
  5. typedef long long ll;
  6. typedef pair<int, int> ii;
  7. typedef pair<int, ii> iii;
  8.  
  9. template<class T>
  10.     bool minimize(T &a, const T &b) {
  11.         if (a > b) return a = b, true;
  12.         return false;
  13.     }
  14.  
  15. template<class T>
  16.     bool maximize(T &a, const T &b) {
  17.         if (a < b) return a = b, true;
  18.         return false;
  19.     }
  20.  
  21. #define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
  22. #define FORR(i,a,b) for(int i=(a); i>=(b); --i)
  23. #define REP(i, n) for(int i=0; i<(n); ++i)
  24. #define RED(i, n) for(int i=(n)-1; i>=0; --i)
  25. #define MASK(i) (1LL << (i))
  26. #define mp make_pair
  27. #define pb push_back
  28. #define fi first
  29. #define se second
  30. #define all(x) x.begin(), x.end()
  31. #define task "robot"
  32.  
  33. const int MOD = 1e9 + 7;
  34. const int inf = 1e9 + 27092008;
  35. const ll INF = 1e18 + 27092008;
  36. const int N = 2000 + 5;
  37. int n, m, c[N][N], f[N][N];
  38. char a[N][N];
  39. ii nxt[N][N];
  40.  
  41. void init(void) {
  42.     cin >> n >> m;
  43.     FOR(i, 1, n) FOR(j, 1, m) {
  44.         cin >> a[i][j];
  45.         int x = i, y = j;
  46.         if (a[i][j] == 'L') y--;
  47.         if (a[i][j] == 'R') y++;
  48.         if (a[i][j] == 'U') x--;
  49.         if (a[i][j] == 'D') x++;
  50.         nxt[i][j] = mp(x, y);
  51.     }
  52. }
  53.  
  54. void process(void) {
  55.     int ans = 0;
  56.     stack<ii> st;
  57.     FOR(i, 1, n) FOR(j, 1, m) if (c[i][j] == 0) {
  58.         f[i][j] = 1;
  59.         int x = i, y = j;
  60.         int ep = 0;
  61.         bool isCycle = false;
  62.         while(true) {
  63.             c[x][y] = 1;
  64.             st.push(mp(x, y));
  65.             int u, v; tie(u, v) = nxt[x][y];
  66.             if (u <= 0 || u > n || v <= 0 || v > m) break;
  67.             if (c[u][v] == 0) {
  68.                 f[u][v] = f[x][y] + 1;
  69.                 x = u; y = v;
  70.             }
  71.             if (c[u][v] == 1) {
  72.                 isCycle = true;
  73.                 break;    
  74.             }
  75.             if (c[u][v] == 2) {
  76.                 f[x][y] += (ep = f[u][v]);
  77.                 break;
  78.             }
  79.         }
  80.  
  81.         tie(x, y) = st.top();
  82.         ans = max(ans, f[x][y]);
  83.         if (isCycle) ep = f[x][y];
  84.  
  85.         while(!st.empty()) {
  86.             tie(x, y) = st.top(); st.pop();
  87.             c[x][y] = 2;
  88.             f[x][y] = (isCycle ? ep : ++ep);
  89.         }        
  90.     }
  91.     cout << ans << endl;
  92. }
  93.  
  94. int main() {
  95.     ios_base::sync_with_stdio(0);
  96.     cin.tie(0); cout.tie(0);
  97.     if (fopen(task".inp", "r")) {
  98.         freopen(task".inp", "r", stdin);
  99.         freopen(task".out", "w", stdout);
  100.     }
  101.     int tc = 1;
  102. //   cin >> tc;
  103.     while(tc--) {
  104.         init();
  105.         process();
  106.     }
  107.     return 0;
  108. }
  109.  
Success #stdin #stdout 0s 5292KB
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https://ideone.com/zwGyhn
language:
C++ (gcc 8.3)
created:
10 days ago
visibility:
public

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