knuth-morris-pratt

初始化数组f全部置0用于部分匹配表
MARRY(X)
for i=0 to y.size
   while j>0 and x[j]!=y[i]
      j=f[j]
   if x[j]==y[i]
      j=j+1
   if j==x.size
      sum=sum+1
return sum

for i=1 to x.size
   j=f[i]
   while j>0 and x[j]!=x[i]
      j=f[j]
   if x[j]==x[i]
      f[i+1]=j+1
   else f[i+1]=0