题目链接：http://codeforces.com/problemset/problem/698/A
很久很久没做咯~~~~
dp 是个很神奇的东西。。。。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstdlib> 4 #include <cstring> 5 using namespace std; 6 7 const int max_day = 100 + 5; 8 const int max_option = 3; 9 10 int dp[max_day][max_option]; 11 // 0:rest 1:contest/rest 12 // 2:sport/rest 3:sport/contest/rest 13 14 int main() 15 { 16 int n, a; 17 #ifndef ONLINE_JUDGE 18 freopen("in.txt", "r", stdin); 19 #endif // ONLINE_JUDGE 20 while (scanf("%d", &n) != EOF) { 21 memset(dp, 0, sizeof(dp)); 22 23 for (int i = 1; i <= n; i++) { 24 scanf("%d", &a); 25 26 // 呢个野要时时刻刻更新，选择最优来更新，甘样就保证到 dp[i][1]和dp[i][2]都系最好噶啦 27 dp[i][0] = max(dp[i-1][0], max(dp[i-1][1], dp[i-1][2])); 28 if (a == 1 || a == 3) { 29 dp[i][1] = max(dp[i-1][2], dp[i-1][0]) + 1; // +1 写出边，重要的事情说3遍！！！ 30 } 31 32 if (a == 2 || a == 3) { 33 dp[i][2] = max(dp[i-1][1], dp[i-1][0]) + 1; 34 } 35 // printf("dp[%d][0]=%d, dp[%d][1]=%d, dp[%d][2]=%d ", i, dp[i][0], i,dp[i][1], i,dp[i][2]); 36 } 37 38 39 printf("%d ", n-max(dp[n][0], max(dp[n][1], dp[n][2]))); 40 41 /* 写错晒了。。。。脑退化 = =，好彩总算知道，dp[i][3] 系无鬼用的，后来知道左，改翻岩呢个细节，靠~ = = 42 for (int i = 1; i <= n; i++) { 43 // dp[i][3] = max(dp[i-1][2], dp[i-1][1]) + 1; 44 if (a[i] == 1) { // contest 45 dp[i][0] = dp[i][1] = dp[i-1][2]+1; 46 dp[i][2] = dp[i-1][2]; 47 } 48 else if (a[i] == 2) { // sport 49 dp[i][0] = dp[i][2] = dp[i-1][1]+1; 50 dp[i][1] = dp[i-1][1]; 51 // printf("dp[%d][2] = %d ", i, dp[i][2]); 52 } 53 else if (a[i] == 0) { // rest 54 dp[i][0] = dp[i-1][0]; 55 dp[i][1] = dp[i-1][1]; 56 dp[i][2] = dp[i-1][2]; 57 // printf("dp[%d][0] = %d ", i, dp[i][0]); 58 } 59 else { // a[i] = 3 // s/r/c 60 if (a[i-1] == 2) { 61 dp[i][1] = dp[i-1][1] + 1; 62 dp[i][2] = dp[i-1][2]; 63 dp[i][0] = dp[i-1][0]; 64 } 65 else if (a[i-1] == 1) { 66 dp[i][2] = dp[i-1][2] + 1; 67 dp[i][0] = dp[i-1][0]; 68 dp[i][1] = dp[i-1][1]; 69 } 70 71 72 /* 73 if (a[i-1] == 0) { 74 dp[i][3] = dp[i-1][0]; 75 } 76 else if (a[i-1] == 1) { 77 dp[i][3] = dp[i-1][2]+1; 78 } 79 else if (a[i-1] == 2) { 80 dp[i][3] = dp[i-1][1]+1; 81 } 82 else { 83 dp[i][3] = max(dp[i-1][2], dp[i-1][1]) + 1; 84 } 85 86 // 87 88 } 89 printf("dp[%d][0] = %d ", i, dp[i][0]); 90 printf("dp[%d][1] = %d ", i, dp[i][1]); 91 printf("dp[%d][2] = %d ", i, dp[i][2]); 92 } 93 printf(" dp[%d][0]=%d, dp[%d][1]=%d, dp[%d][2]=%d ", n, dp[n][0], n,dp[n][1], n,dp[n][2]); 94 */ 95 } 96 return 0; 97 98 }