poj2417

OnlineJudges/poj/2417.cpp

@@ -0,0 +1,67 @@
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+typedef long long i64;
+void exgcd(i64 a, i64 b, i64 &x, i64 &y)
+{
+    b == 0 ? (x = 1, y = 0) : (exgcd(b, a % b, y, x), y -= (a / b) * x);
+}
+struct HashTable
+{
+    static const size_t sz = 500009;
+    i64 idx[sz], val[sz];
+    void init()
+    {
+        memset(idx, -1, sizeof(idx));
+        memset(val, -1, sizeof(val));
+    }
+    void insert(i64 i, i64 v)
+    {
+        i64 j = i % sz;
+        while (idx[j] != -1 && idx[j] != i)
+        {
+            j++;
+            if (j == sz)
+                j = 0;
+        }
+        if (val[j] == -1)
+        {
+            idx[j] = i;
+            val[j] = v;
+        }
+    }
+    i64 find(i64 i)
+    {
+        i64 j = i % sz;
+        while (idx[j] != -1 && idx[j] != i)
+        {
+            j++;
+            if (j == sz)
+                j = 0;
+        }
+        return val[j];
+    }
+} H;
+int main()
+{
+    for (i64 a, b, c; ~scanf("%lld%lld%lld", &c, &a, &b) && a | b | c;)
+    {
+        H.init();
+        i64 m = i64(ceil(sqrt(c))), d = 1;
+        for (int i = 0; i < m; i++, d = d * a % c)
+            H.insert(d, i);
+        i64 res = 1, x, y;
+        bool flag = false;
+        for (i64 i = 0; i < m && !flag; i++, res = res * d % c)
+        {
+            exgcd(res, c, x, y);
+            x = (x * b % c + c) % c;
+            i64 j = H.find(x);
+            if (j != -1)
+                printf("%lld\n", i * m + j), flag = true;
+        }
+        if (!flag)
+            puts("no solution");
+    }
+    return 0;
+}