“无论哪场比赛，都要相信题目是水的”
这不仅是HNOI2018D2T3的教训，也是这题的教训，思维定势真的很可怕。
普及组水题，真是愧对CTSC的头衔。
A当作1，B当作-1，开个桶计数即可。
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 #define rep(i,l,r) for (int i=(l); i<=(r); i++) 5 using namespace std; 6 7 const int M=40000005; 8 bool p[M]; 9 int cnt[M],A[M],B[M],seed,n,k,T,S,ans1,ans2,ans3; 10 11 int getrand(){ 12 seed = ((seed * 12321) ^ 9999) % 32768; 13 return seed; 14 } 15 16 void generateData(){ 17 scanf("%d%d%d",&k,&seed,&S); 18 int t = 0; 19 n = k * 2 + 1; 20 memset(p, 0, sizeof(p)); 21 for (int i = 1; i <= n; i++) 22 { 23 p[i] = (getrand() / 128) % 2; 24 t += p[i]; 25 } 26 int i = 1; 27 while (t > k) 28 { 29 while (p[i] == 0) 30 i++; 31 p[i] = 0; 32 t--; 33 } 34 while (t < k) 35 { 36 while (p[i] == 1) 37 i++; 38 p[i] = 1; 39 t++; 40 } 41 } 42 43 int main(){ 44 freopen("cipher.in","r",stdin); 45 freopen("cipher.out","w",stdout); 46 generateData(); 47 rep(i,1,n) p[i+n]=p[i]; 48 A[0]=n+1; rep(i,1,n<<1) A[i]=A[i-1]+(p[i]?1:-1); 49 rep(i,1,n) if(p[i]) cnt[A[i]]++,T+=A[i]>A[0]; 50 rep(i,1,n){ 51 if(p[i]) T-=cnt[A[i]],cnt[A[i]]--; else T+=cnt[A[i]+1]; 52 if(!p[i]){ 53 if(T==0) ans1=i; 54 if(T==S) ans2=i; 55 if(T==k-S) ans3=i; 56 } 57 if (p[i]) cnt[A[i+n]]++,T+=A[i+n]>A[i]; 58 } 59 printf("%d %d %d ",ans1,ans2,ans3); 60 return 0; 61 }