KMP (Knuth–morris–pratt) algorithm

Article string S, string W to look for

Focus: Get int t[] from W

Use the variable c to represent the preceding character in the W that is currently being compared.
I represents the index in T currently being processed,
int[] T = new Int[w.length];
T[0] =-1; T[1] = 0;
A=r; i=2

Example
Array:a b A B c d a b a B a B
Idx:0 1 2 3 4 5 6 7 8 9 10 11

Case 1:w[c] = = w[i-1]--t[i] = ++c; i++;
Case 2:w[c]! = w[i-1] && c>0--C = t[c];
Case 3:w[c]! = w[i-1] && c==0 to t[i] = 0; i++;

Procedure
array:a    b    a    b    c    d    a    B    a    b    a    b
idx    : 0    1    2    3    4    5    6    7    8    9    11

I	2	3	4	5	5	6	7	8	9	10	11
Case	3	1	1	2	3	3	1	1	1	1	2
Pre-c:	0	0	1	2	0	0	0	1	2	3	4
After-c:	0	1	2	0	0	0	1	2	3	4	2
Comparison:	0 & 0	0 & 2	1 & 3	2 & 4	0 & 4	0 & 5	0 & 6	1 & 7	2 & 8	3 & 9	4 & 10

The last Po section of his own written leetcode on the implement STRSTR () code

1  Public classSolution {2      Public intstrStr (String haystack, string needle) {3         if(needle==NULL|| Needle.length () ==0)4             return0;5         intNdlen =needle.length ();6         intHslen =haystack.length ();7 8         if(ndlen==1) {9             intI=0;Ten             Charc = Needle.charat (0); One              while(i<Hslen) { A                 if(Haystack.charat (i) = =c) { -                     returni; -                 } thei++; -             } -             return-1; -         } +  -         int[] T =New int[Ndlen]; +T[0] = 1; AT[1] = 0; at         inti=2, Cnd=0; -          while(i<Ndlen) {  -             if(Needle.charat (CND) ==needle.charat (i-1)) {  -cnd++;  -t[i++] =CND; -}Else if(cnd>0) { inCND =T[CND]; -}Else { tot[i++] = 0; +             } -         } the  *         intNdidx=0, hsidx=0; $          while(hsidx<Hslen) {Panax Notoginseng             if(Haystack.charat (hsidx) = =Needle.charat (NDIDX)) { -hsidx++; thendidx++; +                 if(Ndidx = =Ndlen) { A                     returnhsidx-Ndlen; the                 } +}Else if(T[ndidx]!=-1) { -Ndidx =T[ndidx]; $}Else { $hsidx++; -             } -         } the         return-1; -     }Wuyi}

KMP (Knuth–morris–pratt) algorithm