done the hw3

main.cpp

@@ -1,55 +1,86 @@
+#include <algorithm>
 #include <iostream>
-#include <vector>
+#include <type_traits>
 #include <variant>
+#include <vector>
 
 // 请修复这个函数的定义：10 分
+template <typename T>
 std::ostream &operator<<(std::ostream &os, std::vector<T> const &a) {
-    os << "{";
-    for (size_t i = 0; i < a.size(); i++) {
-        os << a[i];
-        if (i != a.size() - 1)
-            os << ", ";
-    }
-    os << "}";
-    return os;
+  os << "{";
+  for (size_t i = 0; i < a.size(); i++) {
+    os << a[i];
+    if (i != a.size() - 1)
+      os << ", ";
+  }
+  os << "}";
+  return os;
 }
 
 // 请修复这个函数的定义：10 分
 template <class T1, class T2>
-std::vector<T0> operator+(std::vector<T1> const &a, std::vector<T2> const &b) {
-    // 请实现列表的逐元素加法！10 分
-    // 例如 {1, 2} + {3, 4} = {4, 6}
+auto operator+(std::vector<T1> const &a, std::vector<T2> const &b) {
+  using T0 = decltype(T1{} + T2{});
+  auto lens = std::min(a.size(), b.size());
+  std::vector<T0> res(lens);
+  if (lens == a.size()) {
+    std::transform(a.begin(), a.end(), b.begin(), res.begin(), std::plus<>());
+  } else {
+    std::transform(b.begin(), b.end(), a.begin(), res.begin(), std::plus<>());
+  }
+  return res;
+  // 请实现列表的逐元素加法！10 分
+  // 例如 {1, 2} + {3, 4} = {4, 6}
 }
 
-template <class T1, class T2>
-std::variant<T1, T2> operator+(std::variant<T1, T2> const &a, std::variant<T1, T2> const &b) {
-    // 请实现自动匹配容器中具体类型的加法！10 分
+template <class T1, class T2, class U>
+std::variant<T1, T2> operator+(std::variant<T1, T2> const &a, const U &b) {
+  using tb = std::decay_t<U>;
+  std::variant<T1, T2> res;
+  if constexpr (std::is_same_v<T1, tb> || std::is_same_v<T2, tb>) {
+    std::visit([&](const auto &x) { res = x + b; }, a);
+  } else if constexpr (std::is_same_v<std::variant<T1, T2>, tb>) {
+
+    std::visit([&](const auto &x, const auto &y) { res = x + y; }, a, b);
+  }
+  return res;
 }
+// template <class T1, class T2>
+// std::variant<T1, T2> operator+(std::variant<T1, T2> const &a,
+//                                std::variant<T1, T2> const &b) {
+
+//   std::variant<T1, T2, decltype(T1{} + T2{})> res{};
+//   std::visit([&](const auto &a, const auto &v) { res = a + b; }, a, b);
+//   return res;
+//   // 请实现自动匹配容器中具体类型的加法！10 分
+// }
 
 template <class T1, class T2>
 std::ostream &operator<<(std::ostream &os, std::variant<T1, T2> const &a) {
-    // 请实现自动匹配容器中具体类型的打印！10 分
+  std::visit([&](const auto &a) { os << a; }, a);
+  return os;
+  // 请实现自动匹配容器中具体类型的打印！10 分
 }
 
 int main() {
-    std::vector<int> a = {1, 4, 2, 8, 5, 7};
-    std::cout << a << std::endl;
-    std::vector<double> b = {3.14, 2.718, 0.618};
-    std::cout << b << std::endl;
-    auto c = a + b;
+  std::vector<int> a = {1, 4, 2, 8, 5, 7};
+  std::cout << a << std::endl;
+  std::vector<double> b = {3.14, 2.718, 0.618};
+  std::cout << b << std::endl;
+  auto c = a + b;
 
-    // 应该输出 1
-    std::cout << std::is_same_v<decltype(c), std::vector<double>> << std::endl;
+  // 应该输出 1
+  std::cout << std::is_same_v<decltype(c), std::vector<double>> << std::endl;
 
-    // 应该输出 {4.14, 6.718, 2.618}
-    std::cout << c << std::endl;
+  // 应该输出 {4.14, 6.718, 2.618}
+  std::cout << c << std::endl;
 
-    std::variant<std::vector<int>, std::vector<double>> d = c;
-    std::variant<std::vector<int>, std::vector<double>> e = a;
-    d = d + c + e;
+  std::variant<std::vector<int>, std::vector<double>> d = c;
+  std::variant<std::vector<int>, std::vector<double>> e = a;
+  d = d + c + e;
 
-    // 应该输出 {9.28, 17.436, 7.236}
-    std::cout << d << std::endl;
+  // 应该输出 {9.28, 17.436, 7.236}
+  std::cout << d << std::endl;
 
-    return 0;
+  return 0;
 }