feat(calc_lib): 优化大数除法, 只实现了整数

calc_lib/include/khl_calc/khl_calc_decimal.h

@@ -17,13 +17,13 @@ public:
 
     std::string divide(std::string x, std::string y);
 
-    const int compare(std::string x, std::string y);
+    int compare(std::string x, std::string y);
 private:
 
     /**
      * 比较两个数字的大小
      */
-    // const int compare(std::string x, std::string y);
+    // int compare(std::string x, std::string y);
 };
 KHL_CALC_NAMESPACE_END
 #endif // _KHL_CALC_DECIMAL_H_
\ No newline at end of file

calc_lib/src/khl_calc/khl_calc_decimal.cpp

@@ -16,7 +16,7 @@ std::string Decimal::add(std::string x, std::string y)
     {
         if (x.size() > y.size())
         {
-            auto len = x.size() - y.size();
+            int len = x.size() - y.size();
             for (int i = 0; i < len; i++)
             {
                 y.insert(0, "0");
@@ -24,7 +24,7 @@ std::string Decimal::add(std::string x, std::string y)
         }
         else
         {
-            auto len = y.size() - x.size();
+            int len = y.size() - x.size();
             for (int i = 0; i < len; i++)
             {
                 x.insert(0, "0");
@@ -39,7 +39,7 @@ std::string Decimal::add(std::string x, std::string y)
      */
     char *sx = const_cast<char *>(x.c_str());
     char *sy = const_cast<char *>(y.c_str());
-    const size_t len = x.size();
+    const int len = x.size();
     auto a = std::make_unique<int[]>(len);
     auto b = std::make_unique<int[]>(len);
 
@@ -54,7 +54,7 @@ std::string Decimal::add(std::string x, std::string y)
     }
 
     /** 计算 */
-    const size_t size = len + 1;
+    const int size = len + 1;
     auto c = std::make_unique<int[]>(size);
 
     for (int i = 0; i < len; i++)
@@ -100,7 +100,7 @@ std::string Decimal::substract(std::string x, std::string y)
     {
         if (x.size() > y.size())
         {
-            auto len = x.size() - y.size();
+            int len = x.size() - y.size();
             for (int i = 0; i < len; i++)
             {
                 y.insert(0, "0");
@@ -108,7 +108,7 @@ std::string Decimal::substract(std::string x, std::string y)
         }
         else
         {
-            auto len = y.size() - x.size();
+            int len = y.size() - x.size();
             for (int i = 0; i < len; i++)
             {
                 x.insert(0, "0");
@@ -137,7 +137,7 @@ std::string Decimal::substract(std::string x, std::string y)
      */
     char *sx = const_cast<char *>(s1.c_str());
     char *sy = const_cast<char *>(s2.c_str());
-    const size_t len = s1.size();
+    const int len = s1.size();
     auto a = std::make_unique<int[]>(len);
     auto b = std::make_unique<int[]>(len);
 
@@ -152,7 +152,7 @@ std::string Decimal::substract(std::string x, std::string y)
     }
 
     /** 计算 */
-    const size_t size = len;
+    const int size = len;
     auto c = std::make_unique<int[]>(size);
     for (int i = 0; i < len; i++)
     {
@@ -197,8 +197,8 @@ std::string Decimal::multiply(std::string x, std::string y)
      */
     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;
+    const int la = x.size() + 1;
+    const int lb = y.size() + 1;
     auto a = std::make_unique<int[]>(la);
     auto b = std::make_unique<int[]>(lb);
 
@@ -213,7 +213,7 @@ std::string Decimal::multiply(std::string x, std::string y)
     }
 
     /** 计算 */
-    const size_t lc = x.size() + y.size() + 1;
+    const int lc = x.size() + y.size() + 1;
     auto c = std::make_unique<int[]>(lc);
     for (int i = 1; i < la; i++)
     {
@@ -254,6 +254,12 @@ std::string Decimal::divide(std::string x, std::string y)
         return "1";
     }
 
+    // 除数为 1 , 直接返回被除数
+    if (0 == y.compare("1"))
+    {
+        return x;
+    }
+
     std::string str = "0";
     std::string remainder;
     // 被除数只比除数多一位, 则使用减法
@@ -271,22 +277,30 @@ std::string Decimal::divide(std::string x, std::string y)
     {
         // 被除数比除数多两位或以上, 先用加法再用减法
         // 余数
-        str = "1";
+        str = "0";
+        std::string times = "1";
         std::string num = y;
-        while (compare(num, x) <= 0)
+        std::string t = x;
+        while (t.size() - y.size() >= 2)
         {
-            remainder = num;
-            num = add(num, num);
-            if (compare(num, x) > 0)
+            while (compare(num, t) <= 0)
             {
-                break;
+                remainder = num;
+                num = add(num, num);
+                if (compare(num, t) >= 0)
+                {
+                    num = y;
+                    str = add(str, times);
+                    times = "1";
+                    t = substract(t,remainder);
+                    break;
+                }
+                times = multiply(times, "2");
             }
-            str = multiply(str, "2");
         }
-
-        if (compare(num, x) > 0)
+        remainder = t;
+        if (compare(remainder, y) >= 0)
         {
-            remainder = substract(x,remainder);
             while (compare(remainder, y) >= 0)
             {
                 remainder = substract(remainder, y);
@@ -298,7 +312,7 @@ std::string Decimal::divide(std::string x, std::string y)
     return str;
 }
 
-const int Decimal::compare(std::string x, std::string y)
+int Decimal::compare(std::string x, std::string y)
 {
     if (x.size() < y.size())
     {

calc_lib/src/main/main.cpp

@@ -9,7 +9,7 @@ int main()
     // {
 
         // std::cout << decimal->divide("531518", "123") << std::endl;
-        std::cout << decimal->divide("111", "9") << std::endl;
+        std::cout << decimal->divide("222", "2") << std::endl;
         std::cout << "===================" << std::endl;
     // }
     return 0;

calc_lib/test/testmain.cpp

@@ -50,7 +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("111", "9") << std::endl;
+    std::cout << decimal->divide("222", "2") << std::endl;
 
 }