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KMP_algo.cpp
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KMP_algo.cpp
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#include <bits/stdc++.h>
using namespace std;
#define int long long
#define mod (int)(1e9+7)
#define inf (int)(1e18)
#define sz(s) (int)s.size()
#define all(v) (v).begin(),(v).end()
#define fill(dp) memset(dp,-1,sizeof(dp))
#define input(v) for (auto &i : v) cin >> i;
#define print(v) for (auto &j : v) cout << j << " "; cout << "\n";
void solve() {
string p,t;
cin>>p>>t;
int n = sz(t),m = sz(p);
vector<int>pre(m);
//pre[i] represents the length of longest string which is suffix as well as
//prefix of [t0---ti]
pre[0] = 0;
for(int i=1;i<m;i++) {
int j = pre[i-1];
while(j>0 and p[i]!=p[j]) {
j = pre[j-1];
}
if(p[j]==p[i]) j++;
pre[i] = j;
}
int cnt = 0;
for(int i=0,j=0;i<n;i++) {
while(j>0 and t[i]!=p[j]) j = pre[j-1];
if(t[i]==p[j]) j++;
if(j==m) {
cnt++;
j = pre[j-1];
}
}
cout<<cnt<<"\n";
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int testcases=1;
//cin>>testcases;
while(testcases--) solve();
return 0;
}