首页 > 代码库 > KMP算法 - 字符串匹配的简单运用 --- HDU 1711
KMP算法 - 字符串匹配的简单运用 --- HDU 1711
Number Sequence
Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 11606 Accepted Submission(s): 5294
Problem Description
Given two sequences of numbers : a[1], a[2], ...... , a[N], and b[1], b[2], ...... , b[M] (1 <= M <= 10000, 1 <= N <= 1000000). Your task is to find a number K which make a[K] = b[1], a[K + 1] = b[2], ...... , a[K + M - 1] = b[M]. If there are more than one K exist, output the smallest one.
Input
The first line of input is a number T which indicate the number of cases. Each case contains three lines. The first line is two numbers N and M (1 <= M <= 10000, 1 <= N <= 1000000). The second line contains N integers which indicate a[1], a[2], ...... , a[N]. The third line contains M integers which indicate b[1], b[2], ...... , b[M]. All integers are in the range of [-1000000, 1000000].
Output
For each test case, you should output one line which only contain K described above. If no such K exists, output -1 instead.
Sample Input
2
13 5
1 2 1 2 3 1 2 3 1 3 2 1 2
1 2 3 1 3
13 5
1 2 1 2 3 1 2 3 1 3 2 1 2
1 2 3 2 1
Sample Output
6
Mean:
给你s1,s2两个串，让你找到s2在s1中出现的第一个位置。
analyse:
KMP字符串水题，用c++写的，其实真正理解了KMP算法后，你会发现一点都不难。
Time complexity：O(n) 抓住：主串不回溯
Source code：
// Memory Time// 1347K 0MS// by : Snarl_jsb// 2014-09-28-14.33#include<algorithm>#include<cstdio>#include<cstring>#include<cstdlib>#include<iostream>#include<vector>#include<queue>#include<stack>#include<map>#include<string>#include<climits>#include<cmath>#define N 1000010#define LL long longusing namespace std;int n,m;vector<int> a,b;vector<int> next;void GetNext(){ int k=0; int len=b.size(); next.push_back(0); for(int i=1;i<len;++i) { while(k!=0&&b[i]!=b[k]) k=next[k-1]; if(b[i]==b[k]) k++; next.push_back(k); }// for(int i=0;i<next.size();++i)// cout<<next[i]<<endl;}void KMP(){ GetNext(); bool flag=0; int asize=a.size(),bsize=b.size(),k=0; for(int i=0;i<asize;++i) { while(k>0&&a[i]!=b[k]) { k=next[k-1]; } if(a[i]==b[k]) k++; if(k==m) { cout<<i-m+2<<endl; flag=1; break; } } if(!flag) puts("-1");}int main(){ ios_base::sync_with_stdio(false); cin.tie(0);// freopen("C:\\Users\\ASUS\\Desktop\\cin.cpp","r",stdin);// freopen("C:\\Users\\ASUS\\Desktop\\cout.cpp","w",stdout); int t,tmp; cin>>t; while(t--) { cin>>n>>m; a.clear(),b.clear(),next.clear(); for(int i=0;i<n;++i) { cin>>tmp; a.push_back(tmp); } for(int i=0;i<m;++i) { cin>>tmp; b.push_back(tmp); } KMP(); } return 0;}
KMP算法 - 字符串匹配的简单运用 --- HDU 1711
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