add file

src/168.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+char *convertToTitle(int columnNumber)
+{
+    char *ret = malloc(2);
+    int size = 1;
+
+    while (columnNumber > 0)
+    {
+        columnNumber--;
+        const int mod = columnNumber % 26;
+        columnNumber /= 26;
+        ret[size - 1] = 'A' + mod;
+
+        size++;
+        ret = realloc(ret, size + 1);
+    }
+
+    ret[size - 1] = '\0';
+
+    for (int i = 0, j = size - 2; i < j; i++, j--)
+    {
+        const char tmp = ret[i];
+        ret[i] = ret[j];
+        ret[j] = tmp;
+    }
+
+    return ret;
+}
+
+int main()
+{
+    char *ans = convertToTitle(2147483647);
+    printf("%s\n", ans);
+    free(ans);
+    return 0;
+}