Codeforces750E

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Codeforce 750E

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#include <bits/stdc++.h>//codeforce 750E(https://codeforces.com/contest/750/problem/E)
using namespace std;
const int maxn = 1000050;
typedef pair<int, int> P;
typedef long long ll;
const int inf = 0x3f3f3f3f;
char S[maxn];
int g[maxn][5][5];
char str[6] = "2019";
int ans[5];
int pa(int i, int j, char c) // 
{
    if (i == 4)
        return c == '8';
    if (j > i + 1)
        return inf;
    if (i < j)
    {
        if (c != str[i])
            return inf;
        return 0;
    }
    if (i == 3 && c == '8')
        return 1;
    return c == str[i];
}

void init(int k, int l, int r) // 初始化线段树，线段树节点维护的内容是
{
    if (l == r)
    {
        for (int i = 0; i <= 4; ++i)
            for (int j = i; j <= 4; ++j)
                g[k][i][j] = pa(i, j, S[l - 1]);
        return;
    }
    int mid = (l + r) / 2, ls = k * 2, rs = k * 2 + 1;
    init(ls, l, mid);
    init(rs, mid + 1, r);
    for (int i = 0; i <= 4; i++)
        for (int j = i; j <= 4; j++)
        {
            g[k][i][j] = inf;
            for (int k1 = i; k1 <= j; k1++)
            {
                int l1 = g[ls][i][k1];
                int r1 = g[rs][k1][j];
                g[k][i][j] = min(g[k][i][j], l1 + r1);
            }
        }
}

void query(int k, int s, int e, int l, int r)
{
    if (l <= s && e <= r)
    {
        int aa[5];
        for (int i = 0; i <= 4; i++)
        {
            aa[i] = inf;
            for (int j = 0; j <= i; j++)
                aa[i] = min(aa[i], ans[j] + g[k][j][i]);
        }
        for (int i = 0; i <= 4; i++)
            ans[i] = aa[i];
        return;
    }
    int mid = (s + e) / 2, ls = k * 2, rs = k * 2 + 1;
    if (l <= mid)
        query(ls, s, mid, l, r);
    if (r > mid)
        query(rs, mid + 1, e, l, r);
}

char s[maxn];

int main()
{
    int n,m,i,l,r;
    scanf("%d %d %s", &n, &m, s);
    for(int i=0; i<n; i++)
        S[i]=s[n-i-1];

    init(1, 1, n);
    
    while (m--)
    {
        scanf("%d%d", &l, &r);
        l=n-l+1;
        r=n-r+1;
        swap(l,r);
        for (i = 0; i <= 4; i++)
            ans[i] = inf;
        ans[0] = 0;
        query(1, 1, n, l, r);
        if(ans[4]>n)
            printf("-1\n");
        else
            printf("%d\n",ans[4]);
        //printf("%d\n", ans[4] > n ? -1 : ans[4]);
    }
    return 0;
}

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//codeforce 750E(https://codeforces.com/contest/750/problem/E)
#include <bits/stdc++.h>
#define N 200005
#define inf 0x3f3f3f3f
#define lc (p << 1)
#define rc (p << 1 | 1)
#define mid (T[p].l + T[p].r >> 1)
using namespace std;
struct Node
{
    int l, r, f[5][5];
    inline void create(int x) //初始化线段树
    {
        for (int i = 0; i <= 4; ++i)
            for (int j = 0; j <= 4; ++j)
                f[i][j] = (i == j ? 0 : inf);
        //用f[i][j]表示从状态i转移到状态j所需的最小费用
        switch (x)
        {
        case -1:
        {
            for (int i = 0; i <= 4; ++i)
                f[i][i] = inf;
            break;
        }
        case 2:
        {
            f[0][0] = 1, f[0][1] = 0;
            break;
        }
        case 0:
        {
            f[1][1] = 1, f[1][2] = 0;
            break;
        }
        case 1:
        {
            f[2][2] = 1, f[2][3] = 0;
            break;
        }
        case 7:
        {
            f[3][3] = 1, f[3][4] = 0;
            break;
        }
        case 6:
        {
            f[3][3] = 1, f[4][4] = 1;
            break;
        }
        }
    }
} T[N << 2];
int n, m, num[N];
char s[N];
inline Node merge(Node a, Node b)
{
    Node ret;
    ret.create(-1);
    ret.l = a.l, ret.r = b.r;
    for (int i = 0; i <= 4; ++i)
        for (int j = 0; j <= 4; ++j)
            for (int k = 0; k <= 4; ++k)
                ret.f[i][j] = min(ret.f[i][j], a.f[i][k] + b.f[k][j]);
    return ret;
}
inline void build(int p, int l, int r)
{
    T[p].l = l, T[p].r = r;
    if (l == r)
    {
        T[p].create(num[l]);
        return;
    }
    build(lc, l, mid), build(rc, mid + 1, r);
    T[p] = merge(T[lc], T[rc]);
}
inline Node query(int p, int ql, int qr)
{
    if (ql <= T[p].l && T[p].r <= qr)
        return T[p];
    if (qr <= mid)
        return query(lc, ql, qr);
    if (ql > mid)
        return query(rc, ql, qr);
    return merge(query(lc, ql, mid), query(rc, mid + 1, qr));
}
int main()
{
    scanf("%d%d%s", &n, &m, s + 1);
    for (int i = 1; i <=n; ++i)
        num[i] = s[i] - '0';
    // for(int i=1 ;i<=n ;++i)
    //     printf("%d",num[i]);
    //     puts("");
    build(1, 1, n);
    while (m--)
    {
        int l, r;
        scanf("%d%d", &l, &r);
        // l = n + 1 - l;
        // r = n + 1 - r;
        // swap(l, r);
        // cout << l << ' ' << r << endl;
        Node ans = query(1, l, r);
        printf("%d\n", ans.f[0][4] == inf ? -1 : ans.f[0][4]);
    }
    return 0;
}
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