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 = ;
     char c = getchar();
     while(c < '' || c > '') c = getchar();
     while(c >= '' && c <= '') {
         x = x *  + c - ;
         c = getchar();
     }
     return;
 }

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

 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 = ;
     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 - ] * pw[r - l + ];
 }

 inline void getHash() {
     pw[] = ;
     for(register int i = ; i <= n; i++) {
         pw[i] = B * pw[i - ];
         h[i] = h[i - ] * B + str[i];
     }
     for(register int i = ; i + k -  <= n; i++) {
         uLL t = Hash(i, i + k - );
         //printf("i = %d t = %llu \n", i, t);
         val[i] = Map::insert(t);
         //printf("val %d = %d \n", 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 + );
     int T = (double)n / sqrt(m);
     for(register int i = ; i <= m; i++) {
         read(ask[i].l); read(ask[i].r);
         ask[i].r = std::min(ask[i].r, n - k + );
         ask[i].id = i;
     }
     for(register int i = ; i <= n; i++) fr[i] = (i - ) / T + ;
     std::sort(ask + , ask + m + );
     getHash();

     int l = , r = ; bin[val[]] = ;
     for(register int i = ; i <= m; i++) {
         if(ask[i].l >= ask[i].r) {
             ans[ask[i].id] = ;
             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 = ; i <= m; i++) printf("%lld\n", ans[i]);
     return ;
 }

AC代码