洛谷P5112 FZOUTSY

卡map还行.....手写hash表即可。

我一开始以为这个k会变......在sam上想各种奇技淫巧。

k不变就是问一段区间有多少对长度为k的子串相同。

然后hash把子串转化为数字，就是区间有多少对相同数字。直接莫队即可。

#include <bits/stdc++.h>

inline void read(int &x) {
    x = 0;
    char c = getchar();
    while(c < '0' || c > '9') c = getchar();
    while(c >= '0' && c <= '9') {
        x = x * 10 + c - 48;
        c = getchar();
    }
    return;
}

typedef long long LL;
typedef unsigned long long uLL;
const int N = 3000010;
const uLL B = 13331;

uLL h[N], pw[N];
std::map<uLL, int> mp;
int n, k, val[N], fr[N], bin[N];
char str[N];
LL ans[N], Ans;

namespace Map {
    const int mod = 10000010;
    struct Edge {
        uLL val;
        int num, nex;
    }edge[N]; int tp;
    int e[mod], num;
    inline int insert(uLL v) {
        int x = v % mod;
        for(int i = e[x]; i; i = edge[i].nex) {
            if(edge[i].val == v) return edge[i].num;
        }
        edge[++tp].val = v;
        edge[tp].num = ++num;
        edge[tp].nex = e[x];
        e[x] = tp;
        return num;
    }
}

struct Ask {
    int l, r, id;
    inline bool operator <(const Ask &w) const {
        if(fr[l] != fr[w.l]) return l < w.l;
        return r < w.r;
    }
}ask[N];

inline uLL Hash(int l, int r) {
    return h[r] - h[l - 1] * pw[r - l + 1];
}

inline void getHash() {
    pw[0] = 1;
    for(register int i = 1; i <= n; i++) {
        pw[i] = B * pw[i - 1];
        h[i] = h[i - 1] * B + str[i];
    }
    for(register int i = 1; i + k - 1 <= n; i++) {
        uLL t = Hash(i, i + k - 1);
        //printf("i = %d t = %llu 
", i, t);
        val[i] = Map::insert(t);
        //printf("val %d = %d 
", i, val[i]);
    }
    return;
}

inline void add(int x) {
    Ans += bin[val[x]];
    bin[val[x]]++;
    return;
}

inline void del(int x) {
    bin[val[x]]--;
    Ans -= bin[val[x]];
    return;
}

int main() {
    int m;
    read(n); read(m); read(k);
    scanf("%s", str + 1);
    int T = (double)n / sqrt(m);
    for(register int i = 1; i <= m; i++) {
        read(ask[i].l); read(ask[i].r);
        ask[i].r = std::min(ask[i].r, n - k + 1);
        ask[i].id = i;
    }
    for(register int i = 1; i <= n; i++) fr[i] = (i - 1) / T + 1;
    std::sort(ask + 1, ask + m + 1);
    getHash();

    int l = 1, r = 1; bin[val[1]] = 1;
    for(register int i = 1; i <= m; i++) {
        if(ask[i].l >= ask[i].r) {
            ans[ask[i].id] = 0;
            continue;
        }
        while(ask[i].l < l) {
            add(--l);
        }
        while(r < ask[i].r) {
            add(++r);
        }
        while(l < ask[i].l) {
            del(l++);
        }
        while(ask[i].r < r) {
            del(r--);
        }
        ans[ask[i].id] = Ans;
    }
    for(register int i = 1; i <= m; i++) printf("%lld
", ans[i]);
    return 0;
}