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Tags: KMP

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`**number Sequence**problem Descriptiongiven BothSequences ofNumbers:a[1],a[2], ...... ,a[N], andb[1], b[2], ..., B[m] (1<= M <=10000,1<= N <=1000000). Your task is toFinda NumberK which makea[K] = b[1],a[K +1] = b[2], ...... ,a[K + M-1] = B[m]. If there is more than OneK exist, output theSmallest One. Inputthe First Line ofInput isa NumberT which indicate the Number ofCases. each Case contains three Lines. The First LineIs BothNumbers N andJ O1<= M <=10000,1<= N <=1000000). TheSecond Line containsN integers which indicatea[1],a[2], ...... ,a[N]. TheThird Line containsM integers which indicate b[1], b[2], ..., b[m]. All integers isinch theRange of[-1000000,1000000]. Outputfor eachTest Case, you should output One LineWhich only contain K described above. If No such K exists, output-1instead. Sample Input2 - 51 2 1 2 3 1 2 3 1 3 2 1 21 2 3 1 3 - 51 2 1 2 3 1 2 3 1 3 2 1 21 2 3 2 1Sample Output6-1`

The main idea: first give you a number T, indicating that there is a T group of data, and then give you two numbers, M and N, respectively, the target string s and the number of matched string p, and then the number of M and N, respectively, to find the first number of the first to match the subscript of success: for example

13 5

1 2 1 2 3 1 2 3 1 3 2 1 2

1 2 3) 1 3

When i = = 6 when the match is successful, if not found on the output-1;

Problem-Solving ideas: KMP algorithm, the key is to find the next array of values, the idea of KMP algorithm is: In the matching process, if a mismatch occurs, if NEXT[J] >= 0, then the target string of the pointer I will not change, the pointer of the pattern string J moved to the Next[j] position to continue to match If next[j]=-1, move I to the right 1 bits and J 0 to continue the comparison.

Here's an example:

P a B a B a

J 0 1 2 3 4

NEXT[J]-1 0 0 1 2

Now on the code:

`#include <iostream>#include <cstring>#include <cstdio>using namespace Std;int mN/*int BF (char *s, char *p)//This is a violent do, of course, not advocated, but can refer to (string, hey, I did not change) {int i,j; i = 0; while (I < strlen (s)) {j = 0; while (S[i]==p[j] && J<strlen (p)) {i++; j + +; } if (j = = strlen (p)) return I-strlen (p); i = i-j+1; //I backtrack} return-1;} */void Getnext (int *p,int *next)//key is this {intj =0;intK =-1;Next[0] = -1; while(J < N) {if(k==-1|| P[j]==p[k]) {j + +; k++;Next[j] = k; }ElseK =Next[K]; }}intKMP (int *s,int *p){int Next[10010];inti =0;intj =0; Getnext (P,Next); while(I <m) {if(j==-1||s[I]==p[j]) {i++; j + +; }Elsej =Next[j];if(j = = N)returnI-n +1; }return-1;}int s[1000000+5],p[1000000+5];intMain () {intT scanf"%d", &t); while(t--) {scanf ("%d%d",&m, &n); for(intI=0; i<m; i++) scanf ("%d",&s[i]); for(intI=0; i<n; i++) scanf ("%d", &p[i]);printf("%d\ n", KMP (s, p)); }return 0;}`

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Hdu 1711 number Sequence