简单题
View Code #include < iostream > #include < cstdio > #include < cstdlib > #include < cstring > #include < cmath > using namespace std; #define maxn 100005 bool is [maxn]; long long prm[maxn]; int n, a, b, m, p, q; int getprm( int n){ int i, j, k = 0 ; int s, e = ( int ) (sqrt( 0.0 + n) + 1 ); memset( is , 1 , sizeof ( is )); prm[k ++ ] = 2 ; is [ 0 ] = is [ 1 ] = 0 ; for (i = 4 ; i < n; i += 2 ) is [i] = 0 ; for (i = 3 ; i < e; i += 2 ) if ( is [i]) { prm[k ++ ] = i; for (s = i * 2 , j = i * i; j < n; j += s) is [j] = 0 ; } for (; i < n; i += 2 ) if ( is [i]) prm[k ++ ] = i; return k;} int binarysearch(){ int l = 0 ; int r = n; while (l < r) { int mid = (l + r) / 2 + ((l + r) & 1 ); if ((( long long )prm[mid]) * prm[mid] <= m) l = mid; else r = mid - 1 ; } return l;} void work( int l, int r){ int ans = prm[l] * prm[r]; q = p = prm[l]; while (l >= 0 ) { if (prm[l] * b < a * prm[r]) break ; while (r < n - 1 && prm[l] * b >= a * prm[r + 1 ] && prm[l] * prm[r + 1 ] <= m) r ++ ; if (ans < prm[l] * prm[r]) { p = prm[l]; q = prm[r]; ans = prm[l] * prm[r]; } l -- ; } printf( " %d %d\n " , p, q);} int main(){ // freopen("t.txt", "r", stdin); n = getprm(maxn - 1 ); while (scanf( " %d%d%d " , & m, & a, & b), m | a | b) { int l, r; l = r = binarysearch(); work(l, r); } return 0 ;}