[Ahoi2013]差异

　　后缀数组+单调栈

　　代码

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int N = 501000;

const int MAXN =  N;      

struct SuffixArray{
    int wa[MAXN];          
    int wb[MAXN];            
    int wv[MAXN];           
    int ws[MAXN];          

    int sa[MAXN];           
    int rank[MAXN];        
    int height[MAXN];      
    int r[MAXN];            
    int n;           
    int m;                 

    void input(int *val, int len, int Max){
        for (int i = 0;i < len;i++)
            r[i] = val[i];
        r[len] = 0;                      
        n = len;
        m = Max;
        calSa();
        calHeight();
    }

    int cmp(int *r, int a, int b, int l){
        return (r[a] == r[b] && r[a + l] == r[b + l]);
    }

    void calSa(){                 
        int i, j, p, *x = wa, *y = wb, *t;
        for (i = 0;i < m;i++) ws[i] = 0;
        for (i = 0;i < n + 1;i++) ws[x[i] = r[i]]++;
        for (i = 1;i < m;i++) ws[i] += ws[i - 1];
        for (i = n;i >= 0;i--) sa[--ws[x[i]]] = i;
        for (j = 1, p = 1;p < n + 1;j *= 2, m = p){
            for (p = 0, i = n - j + 1;i < n + 1;i++) y[p++] = i;
            for (i = 0;i < n + 1;i++) if (sa[i] >= j) y[p++] = sa[i] - j;
            for (i = 0;i < n + 1;i++) wv[i] = x[y[i]];
            for (i = 0;i < m;i++) ws[i] = 0;
            for (i = 0;i < n + 1;i++) ws[wv[i]]++;
            for (i = 1;i < m;i++) ws[i] += ws[i - 1];
            for (i = n;i >= 0;i--) sa[--ws[wv[i]]] = y[i];
            for (t = x, x = y, y = t, p = 1, x[sa[0]] = 0, i = 1; i < n + 1;i++)
                x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
        }
    }

    void calHeight(){              
        int i, j, k = 0;
        for (i = 1;i <= n;i++) rank[sa[i]] = i;
        for (i = 0;i < n;height[rank[i++]] = k)
            for (k?k--:0, j = sa[rank[i]- 1];r[i + k] == r[j + k];k++);
    }
   
    int Log[MAXN];
    int best[20][MAXN];
    void initRMQ() {            
        Log[0] = -1;
        for(int i = 1;i <= MAXN;i++){
            Log[i]=(i & (i - 1))?Log[i - 1] : Log[i - 1] + 1 ;
        }
        for(int i = 1; i <= n ; i ++) best[0][i] = height[i];
        for(int i = 1; i <= Log[n] ; i ++) {
            int limit = n - (1<<i) + 1;
            for(int j = 1; j <= limit ; j ++) {
                best[i][j] = (best[i-1][j] > best[i-1][j+(1<<i>>1)]) ? best[i-1][j+(1<<i>>1)] : best[i-1][j];
            }
        }
    }
    int lcp(int a,int b) {      
        a = rank[a];    b = rank[b];
        if(a > b){
            int t = a;
            a = b;
            b = t;
        }
        a ++;
        int t = Log[b - a + 1];
        return (best[t][a] > best[t][b - (1<<t) + 1])? best[t][b - (1<<t) + 1] : best[t][a];
    }
}SA;
int a[N],i,len,top,stack[N];
long long ans,sum;
char s[N];
int main()
{
    scanf("%s",&s);
    len=strlen(s);
    for (i=1;i<=len;i++)
    {
        ans=ans+(long long)i*(len-1);
        a[i-1]=s[i-1];
    }
    SA.input(a,len,200);
    for (i=1;i<=len;i++)
    {
        while (SA.height[i]<SA.height[stack[top]])
        {
            sum=sum-(long long)(stack[top]-stack[top-1])*SA.height[stack[top]];
            top--;
        }
        top++;stack[top]=i;
        sum=sum+(long long)(stack[top]-stack[top-1])*SA.height[stack[top]];
        ans=ans-2*sum;
    }
    printf("%lld
",ans);
}
//3 1 4 2 5 0