Codeforces219c-color stripe DP + greedy

Meaning: N, K, which is a string that has been filled with N colors. You can select K colors, ask how many boxes you need to change at least to make the colors of adjacent boxes different.

Solution: When k = 2, we discuss it separately. We cannot use greed. We can use it in other cases.

Solution code:

1 // file name: 219c. CPP 2 // Author: darkdream 3 // created time: saturday, July 26, 2014, 56 seconds, 4, 5 # include <vector> 6 # include <list> 7 # include <map> 8 # include <set> 9 # include <deque> 10 # include <stack> 11 # include <bitset> 12 # include <algorithm> 13 # include <functional> 14 # include <numeric> 15 # include <utility> 16 # include <sstream> 17 # include <iostream> 18 # include <iomanip> 19 # include <cstdio> 20 # InCl Ude <cmath> 21 # include <cstdlib> 22 # include <cstring> 23 # include <ctime> 24 25 using namespace STD; 26 char STR [1000000]; 27 int main () {28 int N, K; 29 scanf ("% d", & N, & K); 30 scanf ("% s", STR ); 31 int Len = strlen (STR); 32 int sum = 0; 33 If (k = 2) 34 {35 int Tempa, tempb; 36 Tempa = tempb = 0; 37 For (INT I = 0; I <Len; I ++) 38 {39 if (I % 2 = 0) 40 {41 if (STR [I] = 'A') 42 Tempa ++; 43 E LSE tempb ++; 44} else {45 if (STR [I] = 'B') 46 Tempa ++; 47 else tempb ++; 48} 49} 50 if (Tempa <tempb) 51 {52 printf ("% d \ n", Tempa); 53 for (INT I = 0; I <Len; I ++) 54 {55 if (I % 2 = 0) 56 printf ("B"); 57 else printf (""); 58} 59} else {60 printf ("% d \ n", tempb); 61 for (INT I = 0; I <Len; I ++) 62 {63 if (I % 2 = 0) 64 printf ("A"); 65 else printf ("B"); 66} 67 68} 69 return 0; 70} 71 for (INT I = 1; I <Len; I ++) 72 {73 If (STR [I] = STR [I-1]) 74 {75 int OK = 0; 76 for (Int J = 0; j <K; j ++) 77 {78 char T = J + 'a'; 79 if (T! = STR [I-1] & T! = STR [I + 1]) 80 {81 STR [I] = T; 82 OK = 1; 83 break; 84} 85} 86 If (OK = 0) 87 for (Int J = 0; j <K; j ++) 88 {89 char T = J + 'a'; 90 if (T! = STR [I-1]) 91 {92 STR [I] = T; 93 break; 94} 95} 96 sum ++; 97} 98} 99 printf ("% d \ n", sum); 100 puts (STR); 101 return 0; 102}

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