这是 hzwer 巨佬的一场训练赛。
1. 榴莲罐头
单调队列或者纯贪心都是 O(n) ，后者空间是 O(1) 更好……
1 #include <cstdio> 2 #include <deque> 3 4 using namespace std; 5 6 typedef long long LL; 7 8 const LL MOD = 100000007LL; 9 const int _N = 1200000; 10 11 deque<LL> Q; 12 13 LL W[_N]; 14 15 void getnum(LL &num) 16 { 17 char tt; 18 while ((tt = getchar()) < '0' || tt > '9'); 19 num = tt-'0'; 20 while ((tt = getchar()) >= '0' && tt <= '9') 21 num = num*10+tt-'0'; 22 return; 23 } 24 25 int main() 26 { 27 LL N, K, i, ans; 28 getnum(N), getnum(K); 29 ans = 0; 30 for (i = 1; i <= N; ++i) { 31 LL need; 32 getnum(W[i]), getnum(need); 33 while (!Q.empty() && W[Q.back()] >= W[i]) 34 Q.pop_back(); 35 while (!Q.empty() && W[Q.front()]+(i-Q.front())*K >= W[i]) 36 Q.pop_front(); 37 Q.push_back(i); 38 ans = (ans+need*((W[Q.front()]+(i-Q.front())*K%MOD)%MOD)%MOD)%MOD; 39 } 40 printf("%lld ", ans);//m 41 return 0; 42 }
2. 榴莲迷宫
打表找规律。a = min(n, m), b = max(n, m), ans = C(n+m+1, a) + b 。
1 #include <cstdio> 2 #include <algorithm> 3 4 using namespace std; 5 6 typedef long long LL; 7 8 const LL MOD = 1000000007LL; 9 10 LL Mont(LL t0, LL t1) 11 { 12 LL t = 1; 13 t0 %= MOD; 14 while (t1) { 15 if (t1 & 1) t = t*t0%MOD; 16 t1 >>= 1, t0 = t0*t0%MOD; 17 } 18 return t; 19 } 20 21 LL C(LL dn, LL up) 22 { 23 if (dn-up < up) up = dn-up; 24 if (up < 0) return 0; 25 if (up == 0) return 1; 26 LL tmp1 = 1, tmp2 = 1; 27 for (LL i = 1; i <= up; ++i) { 28 tmp1 = tmp1*(dn-i+1)%MOD; 29 tmp2 = tmp2*i%MOD; 30 } 31 return tmp1*Mont(tmp2, MOD-2)%MOD; 32 } 33 34 LL Lucas(LL dn, LL up) 35 { 36 if (dn-up < up) up = dn-up; 37 if (up < 0) return 0; 38 if (up == 0) return 1; 39 return Lucas(dn/MOD, up/MOD)*C(dn%MOD, up%MOD)%MOD; 40 } 41 42 int main() 43 { 44 LL a, b; 45 scanf("%lld%lld", &a, &b); 46 printf("%lld ", (max(a, b)%MOD+Lucas(a+b+1, min(a, b)))%MOD); 47 return 0; 48 }
3. 榴莲……（忘了）
HNOI2015 弹飞绵羊，被强制禁止使用 LCT （其实也不会写）。
写在另一篇题解里 https://www.cnblogs.com/ghcred/p/9297934.html