Добавил свой вариант и тест к ф-ции

histogram.cpp

@@ -42,6 +42,9 @@ vector<size_t> make_histogram(const vector<double>& numbers, size_t bin_count) {
             bins[i] = height;
         }
     }
+
+
+
     return bins;
 } 
 

histogram_internal.h

@@ -2,3 +2,4 @@
 #include <vector>
 
 bool find_minmax(const  std::vector<double>& numbers, double& min, double& max);
+int color(int bin, int max_count);

svg.cpp

@@ -19,6 +19,10 @@ svg_end() {
     cout << "</svg>\n";
 }
 
+int color(int bin, int max_count) {
+    int color;
+    return color = round((10 - (bin * 9) / max_count));
+}
 
 void
 svg_text(double left, double baseline, string text) {
@@ -26,7 +30,7 @@ svg_text(double left, double baseline, string text) {
 }
 
 void svg_rect(double x, double y, double width, double height, string stroke, string fill) {
-    cout << "<rect x='" << x << "' y='" << y << "' width='" << width << "' height='" << height << "' stroke='" << stroke << "' fill='" << fill << "'>" << "</rect>";
+    cout << "<rect x='" << x << "' y='" << y << "' width='" << width << "' height='" << height << "' stroke='" << "#" << stroke << stroke << stroke << "' fill='" << "#" << fill << fill << fill << "'>" << "</rect>";
 }
 
 void show_histogram_svg(const vector<size_t>& bins) {
@@ -38,16 +42,20 @@ void show_histogram_svg(const vector<size_t>& bins) {
     const auto BIN_HEIGHT = 30;
     const auto BLOCK_WIDTH = 10;
 
+
     svg_begin(400, 300);
-    //svg_text(20, 20, to_string(bins[0]));
-    //svg_rect(50, 0, bins[0] * 10, 30);
     double top = 0;
+    double max_count = bins[0];
+    for (size_t i = 0; i < bins.size(); i++) {
+        if (bins[i] > max_count)
+            max_count = bins[i];
+    }
     for (size_t bin : bins) {
-        const double bin_width = BLOCK_WIDTH * bin;
+        int temp_color = color(bin, max_count);
+        const double bin_width = (IMAGE_WIDTH - TEXT_WIDTH) * (bin / max_count);
         svg_text(TEXT_LEFT, top + TEXT_BASELINE, to_string(bin));
-        svg_rect(TEXT_WIDTH, top, bin_width, BIN_HEIGHT, "red", "#ffeeee");
+        svg_rect(TEXT_WIDTH, top, bin_width, BIN_HEIGHT, to_string(temp_color), to_string(temp_color));
         top += BIN_HEIGHT;
     }
-
     svg_end();
 }

tests.cpp

@@ -0,0 +1,15 @@
+#include "histogram_internal.h"
+#include <vector>
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+
+int color(int bin, int max_count) {
+    if (max_count == 0) {
+        return 0;
+    }
+    int color;
+    return color = round((10 - (bin * 9) / max_count));
+}

unittest.cpp

@@ -3,7 +3,7 @@
 #include "doctest.h"
 #include "histogram_internal.h"
 
-TEST_CASE("distinct positive numbers") {
+/*TEST_CASE("distinct positive numbers") {
     double min = 0;
     double max = 0;
     find_minmax({ 1, 2 }, min, max);    
@@ -16,4 +16,11 @@ TEST_CASE("distinct positive numbers") {
     find_minmax({ 2, 2, 2, 2 }, min, max);
     CHECK(min == max);
 
+}*/
+
+TEST_CASE("color") {
+    int temp;
+    temp = color(1, 0);
+    CHECK(temp == 0);
 }
+

unittest.vcxproj

@@ -128,6 +128,7 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="histogram.cpp" />
+    <ClCompile Include="tests.cpp" />
     <ClCompile Include="unittest.cpp" />
   </ItemGroup>
   <ItemGroup>

unittest.vcxproj.filters

@@ -21,6 +21,9 @@
     <ClCompile Include="histogram.cpp">
       <Filter>Исходные файлы</Filter>
     </ClCompile>
+    <ClCompile Include="tests.cpp">
+      <Filter>Исходные файлы</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="histogram_internal.h">