feat(calc_lib): 优化大数除法, 只实现了整数

calc_lib/CMakeLists.txt

@@ -6,7 +6,7 @@ project(khl_calc VERSION 1.0.0 LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 
-# set(CMAKE_CONFIGURATION_TYPES Debug)
+set(CMAKE_CONFIGURATION_TYPES Debug)
 
 # 设置 cmake 脚本目录
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)

calc_lib/src/khl_calc/khl_calc_decimal.cpp

@@ -243,46 +243,56 @@ std::string Decimal::multiply(std::string x, std::string y)
 
 std::string Decimal::divide(std::string x, std::string y)
 {
-    if (0 == x.compare("0") || compare(x,y) < 0)
+    // 被除数为 0 或者被除数小于除数, 均返回 0
+    if (0 == x.compare("0") || compare(x, y) < 0)
     {
         return "0";
     }
-
-    if(0 == compare(x,y) )
+    // 相等直接返回 1
+    if (0 == compare(x, y))
     {
         return "1";
     }
 
-    /**
-     * 字符串转换为倒置的 int 数组
-     * x = 123 , y = 4567
-     * x = 321 , y = 7654
-     */
-    char *sx = const_cast<char *>(x.c_str());
-    char *sy = const_cast<char *>(y.c_str());
-    const size_t la = x.size() + 1;
-    const size_t lb = y.size() + 1;
-    auto a = std::make_unique<int[]>(la);
-    auto b = std::make_unique<int[]>(lb);
-
-    for (int i = 1; i < la; i++)
+    std::string str = "0";
+    std::string remainder;
+    // 被除数只比除数多一位, 则使用减法
+    if (x.size() - y.size() < 2)
     {
-        a[la - i] = sx[i - 1] - '0';
+        // 余数
+        remainder = x;
+        while (compare(remainder, y) >= 0)
+        {
+            remainder = substract(remainder, y);
+            str = add(str, "1");
+        }
     }
-
-    for (int i = 1; i < lb; i++)
+    else
     {
-        b[lb - i] = sy[i - 1] - '0';
-    }
-
-    std::string str = "0";
+        // 被除数比除数多两位或以上, 先用加法再用减法
+        // 余数
+        str = "1";
+        std::string num = y;
+        while (compare(num, x) <= 0)
+        {
+            remainder = num;
+            num = add(num, num);
+            if (compare(num, x) > 0)
+            {
+                break;
+            }
+            str = multiply(str, "2");
+        }
 
-    // 余数
-    std::string remainder = x;
-    while (compare(remainder, y) >= 0)
-    {
-        remainder = substract(remainder,y);
-        str = add(str,"1");
+        if (compare(num, x) > 0)
+        {
+            remainder = substract(x,remainder);
+            while (compare(remainder, y) >= 0)
+            {
+                remainder = substract(remainder, y);
+                str = add(str, "1");
+            }
+        }
     }
 
     return str;

calc_lib/src/main/main.cpp

@@ -9,7 +9,7 @@ int main()
     // {
 
         // std::cout << decimal->divide("531518", "123") << std::endl;
-        std::cout << decimal->divide("9999", "2") << std::endl;
+        std::cout << decimal->divide("111", "9") << std::endl;
         std::cout << "===================" << std::endl;
     // }
     return 0;

calc_lib/test/testmain.cpp

@@ -50,10 +50,7 @@ TEST_CASE("test_divide")
 
     // std::cout << decimal->divide("10", "5") << std::endl;
     // std::cout << decimal->divide("531518", "123") << std::endl;
-    std::cout << decimal->divide("9999", "2") << std::endl;
-    std::cout << decimal->divide("99999", "2") << std::endl;
-    std::cout << decimal->divide("999999", "2") << std::endl;
-    std::cout << decimal->divide("9999999", "2") << std::endl;
+    std::cout << decimal->divide("111", "9") << std::endl;
 
 }