Merge pull request #16 from IMEplusplus/tests/fft

Add fft test

Author: samuraiexx

tests/math/fft.test.cpp

@@ -0,0 +1,54 @@
+// @problem_url: https://www.spoj.com/problems/MUL/
+#include<bits/stdc++.h>
+
+using namespace std;
+typedef long double ld;
+const ld PI = acos(-1);
+
+const int N = 2e5;
+
+// @include: math/fft.cpp
+
+int main() {
+  int n;
+  cin >> n;
+
+  while (n--) {
+    string a, b;
+    cin >> a >> b;
+
+    int size = a.size() + b.size();
+    while (size - (size & -size) != 0) size -= size & -size;
+    size *= 2;
+
+    vector<T> va(size);
+    vector<T> vb(size);
+
+    for (int i = 0; i < a.size(); i++) va[a.size() - i - 1].x = a[i] - '0';
+    for (int i = 0; i < b.size(); i++) vb[b.size() - i - 1].x = b[i] - '0';
+
+    multiply(&va[0], &vb[0], size);
+
+    string answer;
+    int goes = 0;
+
+    for (auto c : va) {
+      int x = c.x + 0.5 + goes;
+
+      goes = 0;
+      if (x > 9) {
+        goes = x / 10;
+        x = x % 10;
+      }
+
+      answer.push_back(x + '0');
+    }
+    answer.push_back(goes + '0');
+
+    while (answer.back() == '0') answer.pop_back();
+    if (answer.empty()) answer.push_back('0');
+    reverse(answer.begin(), answer.end());
+
+    cout << answer << endl;
+  }
+}