两道面试题
题目1:要求从N个元素中随机的抽取k个元素,其中N无法确定。很大,只能遍历一次。
题目2:数组A【1...N], 创建一个新的数组,B【1...N], 时间复杂度O(N),使得B【i] = A[1] *...*A[N] / A[i],不能用除法
题目1算法是蓄水池算法,奇妙。
题目2算法是正向遍历一次,反向遍历一次
View Code
p[0] = 1; q[N+1] = 1; for( int i = 1; i <= N; i++) p[i] = p[i-1] * A[i]; for( int i = N; i >= 1; i--) q[i] = q[i+1] * A[i]; p[i] = A[1] *..*A[i] q[i] = A[N]*..*A[i] B[i] = p[i-1] * q[i+1]
posted on 2012-07-13 17:57 more think, more gains 阅读(146) 评论(0) 编辑 收藏 举报