题目传送门
1 /*
2 贪心：当m == 2时，结果肯定是ABABAB或BABABA，取最小改变量；当m > 2时，当与前一个相等时， 改变一个字母
3 同时不和下一个相等就是最优的解法
4 */
5 #include <cstdio>
6 #include <cstring>
7 #include <algorithm>
8 using namespace std;
9
10 const int MAXN = 5e5 + 10;
11 const int INF = 0x3f3f3f3f;
12 char s[MAXN];
13
14 int main(void) { //Codeforces Round #135 (Div. 2) C. Color Stripe
15 //freopen ("C.in", "r", stdin);
16
17 int n, m;
18 while (scanf ("%d%d", &n, &m) == 2) {
19 scanf ("%s", s + 1); int len = strlen (s + 1);
20
21 if (m == 2) {
22 int c1 = 0, c2 = 0;
23 for (int i=1; i<=len; ++i) {
24 if (i & 1) {
25 if (s[i] == 'A') c2++;
26 else c1++;
27 }
28 else {
29 if (s[i] == 'A') c1++;
30 else c2++;
31 }
32 }
33
34 printf ("%d
", min (c1, c2));
35 for (int i=1; i<=len; ++i) {
36 if (i & 1) printf ("%c", (c1 < c2) ? 'A' : 'B');
37 else printf ("%c", (c1 < c2) ? 'B' : 'A');
38 }
39 puts ("");
40 }
41 else {
42 int ans = 0; s[len+1] = s[0] = '@';
43 for (int i=2; i<=len; ++i) {
44 if (s[i] == s[i-1]) {
45 ans++;
46 for (int j=1; j<=m; ++j) {
47 char ch = 'A' + j - 1;
48 if (s[i] == ch || s[i+1] == ch) continue;
49 else {
50 s[i] = ch; break;
51 }
52 }
53 }
54 }
55 printf ("%d
", ans); s[len+1] = ' ';
56 printf ("%s
", s + 1);
57 }
58 }
59
60 return 0;
61 }