zoj 3278 二分 （题库203页）
数组a[] , N， 数组b[] , M ， 寻找第K大的数ai * bj 。 比较简单
typedef long long LL ;
const int maxn = 100008 ;
LL a[maxn] , b[maxn] , k , n , m ;
int ok(LL x){
LL s = 0 , t ;
for(int i = 1 ; i <= n ; i++){
int l = 1 , r = m , mid ;
t = 0 ;
while(l <= r){
mid = (l + r) >> 1 ;
if(x >= a[i] * b[mid]){
t = mid ;
l = mid + 1 ;
}
else r = mid - 1 ;
}
s += t ;
if(s >= k) return 1 ;
}
return s >= k ;
}
int main(){
int i ;
while(scanf("%lld%lld%lld" , &n ,&m ,&k) != EOF){
k = n*m - k + 1 ;
for(i = 1 ; i <= n ; i++) scanf("%lld" , &a[i]) ;
for(i = 1 ; i <= m ; i++) scanf("%lld" , &b[i]) ;
sort(b+1 , b+1+m) ;
LL l , r , mid , s , t ;
l = 0 , r = 10000000000LL ;
while(l <= r){
mid = (l + r) >> 1 ;
if(t = ok(mid)){
s = mid ;
r = mid - 1 ;
}
else l = mid + 1 ;
}
printf("%lld\n" , s) ;
}
return 0 ;
}
typedef long long LL ;
const int maxn = 100008 ;
LL a[maxn] , b[maxn] , k , n , m ;
int ok(LL x){
LL s = 0 , t ;
for(int i = 1 ; i <= n ; i++){
int l = 1 , r = m , mid ;
t = 0 ;
while(l <= r){
mid = (l + r) >> 1 ;
if(x >= a[i] * b[mid]){
t = mid ;
l = mid + 1 ;
}
else r = mid - 1 ;
}
s += t ;
if(s >= k) return 1 ;
}
return s >= k ;
}
int main(){
int i ;
while(scanf("%lld%lld%lld" , &n ,&m ,&k) != EOF){
k = n*m - k + 1 ;
for(i = 1 ; i <= n ; i++) scanf("%lld" , &a[i]) ;
for(i = 1 ; i <= m ; i++) scanf("%lld" , &b[i]) ;
sort(b+1 , b+1+m) ;
LL l , r , mid , s , t ;
l = 0 , r = 10000000000LL ;
while(l <= r){
mid = (l + r) >> 1 ;
if(t = ok(mid)){
s = mid ;
r = mid - 1 ;
}
else l = mid + 1 ;
}
printf("%lld\n" , s) ;
}
return 0 ;
}