题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5461
比赛的时候没敢多想，直接把八个情况全部枚举出来。
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 #include <cmath> 5 using namespace std; 6 7 typedef long long LL; 8 const int INF = 0x3f3f3f3f; 9 const int maxn = 5000000+100; 10 11 int t[maxn]; 12 int n; 13 int a,b; 14 15 int main() { 16 int T; 17 scanf("%d",&T); 18 for(int tt = 1;tt <= T;++tt) { 19 scanf("%d %d %d",&n,&a,&b); 20 for(int i = 1;i <= n;++i) { 21 scanf("%d",&t[i]); 22 } 23 int maxx1 = 0,maxx2 = 0; 24 int mn1 = INF,mn2 = INF; 25 int mm1 = -INF,mm2 = -INF; 26 int nn1 = INF,nn2 = INF; 27 for(int i = 1;i <= n;++i) { 28 if(t[i] > mm1) { 29 mm2 = mm1; 30 mm1 = t[i]; 31 } 32 else if(t[i] > mm2) 33 mm2 = t[i]; 34 35 if(t[i] < nn1) { 36 nn2 = nn1; 37 nn1 = t[i]; 38 } 39 else if(t[i] < nn2) 40 nn2 = t[i]; 41 if(abs(t[i]) > abs(maxx1)) { 42 maxx2 = maxx1; 43 maxx1 = t[i]; 44 } 45 else if(abs(t[i]) > abs(maxx2)) 46 maxx2 = t[i]; 47 48 if(abs(t[i]) < abs(mn1)) { 49 mn2 = mn1; 50 mn1 = t[i]; 51 } 52 else if(abs(t[i]) < abs(mn2)) 53 mn2 = t[i]; 54 55 } 56 LL res1,res2; 57 if(a >= 0) { 58 res1 = (LL)a*maxx1*maxx1; 59 if(b >= 0) { 60 if(mm1 != maxx1) res1 += (LL)b*mm1; 61 else res1+= (LL)b*mm2; 62 } 63 else { 64 if(nn1 != maxx1) res1 += (LL)b*nn1; 65 else res1 += (LL)b*nn2; 66 } 67 } 68 else { 69 res1 = (LL)a*mn1*mn1; 70 if(b >= 0) { 71 if(mm1 != mn1) res1 += (LL)b*mm1; 72 else res1 += (LL)b*mm2; 73 } 74 else { 75 if(nn1 != mn1) res1 += (LL)b*nn1; 76 else res1 += (LL)b*nn2; 77 } 78 } 79 if(b >= 0) { 80 res2 = (LL)b*mm1; 81 if(a >= 0) { 82 if(maxx1 != mm1) res2 += (LL)a*maxx1*maxx1; 83 else res2 += (LL)a*maxx2*maxx2; 84 } 85 else { 86 if(mn1 != mm1) res2 += (LL)a*mn1*mn1; 87 else res2 += (LL)a*mn2*mn2; 88 } 89 } 90 else { 91 res2 = (LL)b*nn1; 92 if(a >= 0) { 93 if(maxx1 != nn1) res2 += (LL)a*maxx1*maxx1; 94 else res2 += (LL)a*maxx2*maxx2; 95 } 96 else { 97 if(mn1 != nn1) res2 += (LL)a*mn1*mn1; 98 else res2 += (LL)a*mn2*mn2; 99 } 100 } 101 102 printf("Case #%d: %I64d ", tt, max(res1,res2)); 103 } 104 return 0; 105 }