problems 3 - 9

2 files changed, 78 insertions, 0 deletions

diff --git a/p4/CMakeLists.txt b/p4/CMakeLists.txt
new file mode 100644
index 0000000..ba228e5
--- /dev/null
+++ b/p4/CMakeLists.txt
@@ -0,0 +1,7 @@
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
+PROJECT(euler_problem4 C)
+INCLUDE_DIRECTORIES(../common)
+SET(SOURCES main.c ../common/utils.c)
+ADD_EXECUTABLE(p4 ${SOURCES})
+TARGET_LINK_LIBRARIES(p4 m)
+SET_SOURCE_FILES_PROPERTIES(${SOURCES} PROPERTIES COMPILE_FLAGS -g)
diff --git a/p4/main.c b/p4/main.c
new file mode 100644
index 0000000..0931535
--- /dev/null
+++ b/p4/main.c
@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "utils.h"
+
+list_t *digits(int i)
+{
+    list_t *lst = NULL;
+
+    while (i > 0)
+    {
+        int digit = i % 10;
+        i = i / 10;
+        lst = list_append_int(lst, digit);
+    }
+
+    return lst;
+}
+
+int is_palindrome(int i)
+{
+    list_t *d = NULL;
+    int len = 0;
+    int j = 0;
+
+    if (i < 10)
+        return 1;
+
+    d = digits(i);
+    len = list_len(d);
+
+    // printf("i:%d\n", i);
+
+    for (j = 0; j < len/2; ++j)
+    {
+        int *a = (int*)list_get_n(d, j);
+        int *b = (int*)list_get_n(d, len-1-j);
+
+        // printf("a:%d b:%d\n", *a, *b);
+
+        if (*a != *b)
+        {
+            return 0;
+        }
+    }
+
+    list_free(d, list_free_int);
+
+    return 1;
+}
+
+int main(int argc, char **argv)
+{
+    int i, j;
+
+    for (i = 999; i >= 900; i--)
+    {
+        for (j = 999; j >= 900; j--)
+        {
+            int k = i*j;
+
+            if (is_palindrome(k))
+            {
+                printf("%d * %d = %d\n", i, j, k);
+                return 0;
+            }
+        }
+    }
+
+    return 0;
+}
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