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  • 《字符串专题》

    查询回文子串个数:

    #include<bits/stdc++.h>
    using namespace std;
    typedef long long LL;
    typedef pair<double,int> pii;
    const int N = 3e5+5;
    const int M = 1e6+5;
    const LL Mod = 1e9+7;
    #define rg register
    #define pi acos(-1)
    #define INF 1e18
    #define CT0 cin.tie(0),cout.tie(0)
    #define IO ios::sync_with_stdio(false)
    #define dbg(ax) cout << "now this num is " << ax << endl;
    namespace FASTIO{
        inline LL read(){
            LL x = 0,f = 1;char c = getchar();
            while(c < '0' || c > '9'){if(c == '-') f = -1;c = getchar();}
            while(c >= '0' && c <= '9'){x = (x<<1)+(x<<3)+(c^48);c = getchar();}
            return x*f;
        }
        void print(int x){
            if(x < 0){x = -x;putchar('-');}
            if(x > 9) print(x/10);
            putchar(x%10+'0');
        }
    }
    using namespace FASTIO;
    
    int len[N];
    int Marchar(string t)
    {
        string s = "@#";
        int mx = 0,cnt = 0,p = 0;
        for(rg int i = 0;i < t.size();++i)
        {
            s += "#";
            s += t[i];
        }
        s += "#";
        for(rg int i = 0;i < s.size();++i)
        {
            if(mx > i) len[i] = min(mx-i,len[2*p-i]);
            else len[i] = 1;
            while(s[i-len[i]] == s[i+len[i]]) len[i]++;
            if(len[i]+i > mx) mx = len[i]+i,p = i;
            cnt += len[i]/2;
        }
        return cnt;
    }
    int main()
    {
        int n;n = read();
        string s;cin >> s;
        int ans = Marchar(s);
        printf("%d
    ",ans);
        system("pause");
        return 0;
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/zwjzwj/p/13769849.html
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