这个题目的思维太巧了,题意就不讲了
E[ i ] = ∑pk * E[i + k] + E[0] * p[0] 而 E[0 ] p[0] 都是常数 ,因为 E[ i ] 的表示中都含有 E[0] 那么干脆 设E[ i ] = a[i] * E[0 ] + b[i] 带入
E[ i ] = ∑pk * E[i + k] + E[0] * p[0] + 1
= ∑pk *( a[i+k]*E[0] + b[i+k] )+ E[0]*p[0] + 1
= ( ∑pk *( a[i+k] + p[0] ) * E[0] + ( ∑pk * b[i+ k] + 1 )
= a[ i ] * E[ 0 ] + b[ i ]
可得递推式: a[ i ] = ( ∑pk *( a[i+k] + p[0] )
b[i ] = ( ∑pk * b[i+ k] + 1 )
推荐个写的很好的博客, http://blog.youkuaiyun.com/morgan_xww/article/details/6775853