Data commit

Task/Four-is-magic/C/four-is-magic.c

@@ -0,0 +1,98 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <glib.h>
+
+typedef struct named_number_tag {
+    const char* name;
+    uint64_t number;
+} named_number;
+
+const named_number named_numbers[] = {
+    { "hundred", 100 },
+    { "thousand", 1000 },
+    { "million", 1000000 },
+    { "billion", 1000000000 },
+    { "trillion", 1000000000000 },
+    { "quadrillion", 1000000000000000ULL },
+    { "quintillion", 1000000000000000000ULL }
+};
+
+const named_number* get_named_number(uint64_t n) {
+    const size_t names_len = sizeof(named_numbers)/sizeof(named_number);
+    for (size_t i = 0; i + 1 < names_len; ++i) {
+        if (n < named_numbers[i + 1].number)
+            return &named_numbers[i];
+    }
+    return &named_numbers[names_len - 1];
+}
+
+size_t append_number_name(GString* str, uint64_t n) {
+    static const char* small[] = {
+        "zero", "one", "two", "three", "four", "five", "six", "seven", "eight",
+        "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
+        "sixteen", "seventeen", "eighteen", "nineteen"
+    };
+    static const char* tens[] = {
+        "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"
+    };
+    size_t len = str->len;
+    if (n < 20) {
+        g_string_append(str, small[n]);
+    }
+    else if (n < 100) {
+        g_string_append(str, tens[n/10 - 2]);
+        if (n % 10 != 0) {
+            g_string_append_c(str, '-');
+            g_string_append(str, small[n % 10]);
+        }
+    } else {
+        const named_number* num = get_named_number(n);
+        uint64_t p = num->number;
+        append_number_name(str, n/p);
+        g_string_append_c(str, ' ');
+        g_string_append(str, num->name);
+        if (n % p != 0) {
+            g_string_append_c(str, ' ');
+            append_number_name(str, n % p);
+        }
+    }
+    return str->len - len;
+}
+
+GString* magic(uint64_t n) {
+    GString* str = g_string_new(NULL);
+    for (unsigned int i = 0; ; ++i) {
+        size_t count = append_number_name(str, n);
+        if (i == 0)
+            str->str[0] = g_ascii_toupper(str->str[0]);
+        if (n == 4) {
+            g_string_append(str, " is magic.");
+            break;
+        }
+        g_string_append(str, " is ");
+        append_number_name(str, count);
+        g_string_append(str, ", ");
+        n = count;
+    }
+    return str;
+}
+
+void test_magic(uint64_t n) {
+    GString* str = magic(n);
+    printf("%s\n", str->str);
+    g_string_free(str, TRUE);
+}
+
+int main() {
+    test_magic(5);
+    test_magic(13);
+    test_magic(78);
+    test_magic(797);
+    test_magic(2739);
+    test_magic(4000);
+    test_magic(7893);
+    test_magic(93497412);
+    test_magic(2673497412U);
+    test_magic(10344658531277200972ULL);
+    return 0;
+}