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  1. // ~~ icebear ~~
  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 BIT(S, i) (((S) >> (i)) & 1)
  27. #define mp make_pair
  28. #define pb push_back
  29. #define fi first
  30. #define se second
  31. #define all(x) x.begin(), x.end()
  32. #define task "icebear"
  33. /*END OF TEMPLATE. ICEBEAR AND THE CAT WILL WIN VOI26 */
  34.  
  35. const int MOD = 1e9 + 7;
  36. const int inf = 1e9 + 27092008;
  37. const ll INF = 1e18 + 27092008;
  38. const int N = 1000 + 5;
  39. int numRow, numCol, val[N][N];
  40. ll f[N][N];
  41.  
  42. void init(void) {
  43.     cin >> numRow; numCol = numRow;
  44.     FOR(i, 1, numRow) FOR(j, 1, numCol) cin >> val[i][j];
  45. }
  46.  
  47. void process(void) {
  48.     memset(f, -0x3f, sizeof f);
  49.     f[1][1] = val[1][1];
  50.     FOR(cross, 2, numRow + numCol) { // i + j
  51.         vector<ii> cells;
  52.         vector<ll> dp, pref, suff, pfmax, sfmax;
  53.         for(int j = min(cross - 1, numCol), i = cross - j; j > 0; j--, i++) {
  54.             cells.pb(mp(i, j));
  55.             dp.pb(f[i][j]);
  56.             pref.pb(val[i][j]);
  57.             suff.pb(val[i][j]);
  58.         }
  59.  
  60.         int sz = (int)pref.size();
  61.         FOR(i, 1, sz - 1) pref[i] += pref[i - 1];
  62.         FORR(i, sz - 2, 0) suff[i] += suff[i + 1];
  63.  
  64.         pfmax.pb(dp[0] - pref[0]);
  65.         sfmax.pb(dp[sz - 1] - suff[sz - 1]);
  66.         FOR(i, 1, sz - 1) pfmax.pb(max(pfmax.back(), dp[i] - pref[i]));
  67.         FORR(i, sz - 2, 0) sfmax.pb(max(sfmax.back(), dp[i] - suff[i]));
  68.         reverse(all(sfmax));
  69.  
  70.         FOR(i, 0, sz - 1) maximize(f[cells[i].fi][cells[i].se], max(pref[i] + pfmax[i], suff[i] + sfmax[i]));
  71.         FOR(i, 0, sz - 1) {
  72.             int x, y; tie(x, y) = cells[i];
  73.             maximize(f[x + 1][y], f[x][y] + val[x + 1][y]);
  74.             maximize(f[x][y + 1], f[x][y] + val[x][y + 1]);
  75.         }
  76.     }
  77.  
  78.     cout << f[numRow][numCol];
  79. }
  80.  
  81. int main() {
  82.     ios_base::sync_with_stdio(0);
  83.     cin.tie(0); cout.tie(0);
  84.     if (fopen(task".inp", "r")) {
  85.         freopen(task".inp", "r", stdin);
  86.         freopen(task".out", "w", stdout);
  87.     }
  88.     int tc = 1;
  89. //    cin >> tc;
  90.     while(tc--) {
  91.         init();
  92.         process();
  93.     }
  94.     return 0;
  95. }
  96.  
Success #stdin #stdout 0.01s 13364KB
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-4485090715960753727
https://ideone.com/6A1sHm
language:
C++14 (gcc 8.3)
created:
22 hours ago
visibility:
public

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