Update README.md

Author: yanglbme

solution/0000-0099/0012.Integer to Roman/README.md

@@ -302,25 +302,26 @@ class Solution {
 
 #### C
 
-```C
-
-char *intToRoman(int num) {
-  static char res[20];
-  res[0] = '\0';
-
-  int vals[] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
-  char *syms[] = {"M",  "CM", "D",  "CD", "C",  "XC", "L",
-                  "XL", "X",  "IX", "V",  "IV", "I"};
-
-  for (int i = 0; i < 13; i++) {
-    while (num >= vals[i]) {
-      strcat(res, syms[i]);
-      num -= vals[i];
+```c
+static const char* cs[] = {
+    "M", "CM", "D", "CD", "C", "XC",
+    "L", "XL", "X", "IX", "V", "IV", "I"};
+
+static const int vs[] = {
+    1000, 900, 500, 400, 100, 90,
+    50, 40, 10, 9, 5, 4, 1};
+
+char* intToRoman(int num) {
+    static char ans[20];
+    ans[0] = '\0';
+    for (int i = 0; i < 13; ++i) {
+        while (num >= vs[i]) {
+            num -= vs[i];
+            strcat(ans, cs[i]);
+        }
     }
-  }
-  return res;
+    return ans;
 }
-
 ```
 
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