mat: det (mint only)

Author: snuke

mat.cpp

@@ -29,4 +29,29 @@ struct Matrix {
     if (t&1) r = r*(*this);
     return r;
   }
+  // https://youtu.be/-j02o6__jgs?t=11273
+  /* mint only
+  mint det() {
+    assert(h == w);
+    mint res = 1;
+    rep(k,h) {
+      for (int i = k; i < h; ++i) {
+        if (d[i][k] == 0) continue;
+        if (i != k) {
+          swap(d[i],d[k]);
+          res = -res;
+        }
+      }
+      if (d[k][k] == 0) return 0;
+      res *= d[k][k];
+      mint inv = mint(1)/d[k][k];
+      rep(j,h) d[k][j] *= inv;
+      for (int i = k+1; i < h; ++i) {
+        mint c = d[i][k];
+        for (int j = k; j < h; ++j) d[i][j] -= d[k][j]*c;
+      }
+    }
+    return res;
+  }
+  //*/
 };