problems 3 - 9

2 files changed, 96 insertions, 0 deletions

diff --git a/p9/CMakeLists.txt b/p9/CMakeLists.txt
new file mode 100644
index 0000000..987dbf1
--- /dev/null
+++ b/p9/CMakeLists.txt
@@ -0,0 +1,7 @@
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
+PROJECT(euler_problem9 C)
+INCLUDE_DIRECTORIES(../common)
+SET(SOURCES main.c ../common/utils.c)
+ADD_EXECUTABLE(p9 ${SOURCES})
+TARGET_LINK_LIBRARIES(p9 m)
+SET_SOURCE_FILES_PROPERTIES(${SOURCES} PROPERTIES COMPILE_FLAGS -g)
diff --git a/p9/main.c b/p9/main.c
new file mode 100644
index 0000000..c75fea9
--- /dev/null
+++ b/p9/main.c
@@ -0,0 +1,89 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int gen(int p, int pmax, int q)
+{
+    int a, b, c;
+
+    for (; p < pmax; p += 2)
+    {
+        int _q = q;
+
+        for (; _q < p; _q += 2)
+        {
+            if (!pythagorean_triplet(p, _q, &a, &b, &c))
+                continue;
+
+            printf("p:%d q:%d a:%d\tb:%d\tc:%d\n", p, _q, a, b, c);
+
+            if (a+b+c == 1000)
+                goto found;
+
+            if (1000 % (a+b+c) == 0)
+            {
+                int m = 1000 / (a+b+c);
+
+                printf("triplet sum (%d) is divisor of 1000, multiply by %d\n",
+                    a+b+c, m);
+
+                a *= m;
+                b *= m;
+                c *= m;
+
+                if (a+b+c == 1000)
+                    goto found;
+            }
+        }
+    }
+
+    return 0;
+
+found:
+
+    printf("got it: a:%d b:%d c:%d a*b*c=%d\n", a, b, c, a*b*c);
+
+    return 1;
+}
+
+int main(int argc, char **argv)
+{
+    // some different ways to generate pythagorean triples, let's hope one of
+    // these yields the result
+
+    if (gen(3, 20, 3))
+        return 0;
+
+    printf("--\n");
+
+    if (gen(3, 20, 2))
+        return 0;
+
+    printf("--\n");
+
+    if (gen(2, 20, 3))
+        return 0;
+
+    // and of course the brute-force way :-) (this could be optimized by
+    // making the condition b<1000 -> b<1000-a and just stating c=1000-a-b
+    // instead of iterating values of c).
+
+    // int a, b, c;
+
+    // for (a = 1; a < 1000; a++)
+    // {
+    //     for (b = a+1; b < 1000; b++)
+    //     {
+    //         for (c = b+1; c < 1000; c++)
+    //         {
+    //             if ((a + b + c == 1000) && (a*a + b*b == c*c))
+    //             {
+    //                 printf("a:%d b:%d c:%d a*b*c:%d\n", a, b, c, a*b*c);
+    //                 return 0;
+    //             }
+    //         }
+    //     }
+    // }
+
+    return 0;
+}
+