Substring (后缀数组 + 计数)

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const int MAXN = 200100;
bool cmp(int *r, int a, int b, int l) {
    return r[a] == r[b] && r[a + l] == r[b + l];
}
int t1[MAXN], t2[MAXN], c[MAXN];

void da(int str[], int sa[], int rk[], int height[], int n, int m) {
    n++;
    int i, j, p, *x = t1, *y = t2;
//第一轮基数排序,如果 s 的最大值很大,可改为快速排序
    for(i = 0; i < m; i++)
        c[i] = 0;
    for(i = 0; i < n; i++)
        c[x[i] = str[i]]++;
    for(i = 1; i < m; i++)
        c[i] += c[i - 1];
    for(i = n - 1; i >= 0; i -- )
        sa[ -- c[x[i]]] = i;
    for(j = 1; j <= n; j <<= 1) {
        p = 0;
//直接利用 sa 数组排序第二关键字
        for(i = n - j; i < n; i++)
            y[p++] = i;//后面的 j 个数第二关键字为空的最小
        for(i = 0; i < n; i++)
            if(sa[i] >= j)
                y[p++] = sa[i] - j;
//这样数组 y 保存的就是按照第二关键字排序的结果
//基数排序第一关键字
        for(i = 0; i < m; i++)
            c[i] = 0;
        for(i = 0; i < n; i++)
            c[x[y[i]]]++;
        for(i = 1; i < m; i++)
            c[i] += c[i - 1];
        for(i = n - 1; i >= 0; i -- )
            sa[ -- c[x[y[i]]]] = y[i];
//根据 sa 和 x 数组计算新的 x 数组
        swap(x, y);
        p = 1;
        x[sa[0]] = 0;
        for(i = 1; i < n; i++)
            x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
        if(p >= n)
            break;
        m = p;//下次基数排序的最大值
    }
    int k = 0;
    n -- ;
    for(i = 0; i <= n; i++)
        rk[sa[i]] = i;
    for(i = 0; i < n; i++) {
        if(k)   k -- ;
        j = sa[rk[i] - 1];
        while(str[i + k] == str[j + k])
            k++;
        height[rk[i]] = k;
    }
}
int rk[MAXN], height[MAXN], sa[MAXN], in[MAXN];
char s[MAXN], t[MAXN];
vector<int>vec;
vector<int>:: iterator it;

int main() {
    int T;scanf("%d", &T);
    for(int ncase = 1; ncase <= T; ncase ++){
        scanf("%s%s",t, s);
        int n = strlen(s);
        vec.clear();
        for(int i = 0; i < n; i ++){
            in[i] = s[i];
            if(s[i] == t[0]) vec.push_back(i);
        }in[n] = 0;
        da(in, sa, rk, height, n, 128);
        ll ans = 0;
        for(int i = 1; i <= n; i ++){
            it = lower_bound(vec.begin(), vec.end(), sa[i]);
            printf("%d %d %d\n", sa[i], *it, height[i]);
            if(it == vec.end()) continue;
            int tmp = n - sa[i] - max(height[i], *it - sa[i]);
            if(tmp > 0) ans += tmp;
        printf("Case #%d: %lld\n",ncase, ans);
        }printf("\n");
    }
    return 0;
}