Codeforces Round #373 (Div. 2)

岑寂了一个暑假之后终于涨分了，借助了A题的hack大法， c题没有理解好题意，wa就放弃了，后来再样例的帮助下。。终于AC

现在还没搞懂矩阵啊。烦。。抄来别人的代码

A. Vitya in the Countryside

当n = 1时候特判0，15

#include <iostream>
#include <cstdio>

using namespace std;
int main() {
    int n, m;
    int a[100];
    scanf("%d", &n);
    for(int i = 0;i < n; i++){
        scanf("%d", &a[i]);
    }
    if(a[n-1] == 15) printf("DOWN\n");
    else if(a[n-1] == 0) printf("UP\n");
    else if(n == 1) printf("-1\n");
    else if(a[n-1] < a[n-2]){
        printf("DOWN\n");
    }else printf("UP\n");
    return 0;
}

B. Anatoly and Cockroaches

分别计算奇偶位r、b的个数，求一下就好

#include <iostream>
#include <cstdio>

using namespace std;
int main() {
    int n, m;
    char s[100002];
    scanf("%d", &n);
    scanf("%s", s);
    int first_r = 0, first_b = 0, second_r = 0, second_b = 0;
    for(int i = 0; i < n; i++){
        if(i%2 == 0) {
            if(s[i] == 'r') first_r++;
            else first_b++;
        }else {
            if(s[i] == 'b') second_b++;
            else second_r++;
        }
    }
    //printf("%d %d %d %d\n", first_r, first_b, second_r, second_b);
    int ans1 = first_b + second_r - min(first_b, second_r);
    int ans2 = first_r + second_b - min(first_r, second_b);
    printf("%d\n", min(ans1, ans2));
    return 0;
}

C. Efim and Strange Grade

搞得我也很恶心了， 分类讨论各个情况

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int main() {
    int n, m;
    scanf("%d%d", &n, &m);
    char s[200005];
    scanf("%s", s);
    int flag = 0, flags = 1;
    int ans = -1;
    for(int i = 0; i < n; i++) {
        if(s[i] == '.') {
            flag = 1;
            continue;
        }
        if(s[i] - '0' >= 5 && flag == 1 && m > 0) {
            ans = i;
            m--;
            break;
        }
    }
    if(ans == -1) printf("%s\n", s);
    else {
        int snow = 1;
        if(s[ans-1] == '.') ans--, flags = 0;
        for(int i = ans-1; i >= 0; i--) {
            if(s[i] == '.') continue;
            int sum = s[i] - '0' + snow;
            s[i] = sum%10 + '0';
            snow = sum/10;
        }
        if(snow == 1) {
            printf("1");
            for(int i = 0; i < ans; i++) printf("%c", s[i]);
            printf("\n");
        } else {
            int last = ans, now = 0;
            for(int i = last-1; i >= 0; i--) {
                if(s[i] == '.') {
                    flags = 0;
                    ans = i-1;
                    continue;
                }
                int sum = s[i] - '0' + now;
               // printf("%d %d %d %d\n", i, now, sum, flags);
                if((sum <= 4 || m <=  0) && flags) {
                    now = 0;
                    s[i] = sum + '0';
                    ans = i;
                    break;
                } else if(flags) {
                    m--;
                    now = 1;
                    ans--;
                } else {
                    s[i] = sum%10 + '0';
                    now = sum /10;
                }
            }
            if(now == 1) {
                printf("1");
                for(int i = 0; i <= ans; i++) printf("%c", s[i]);
                printf("\n");
            }
            else {
            if(s[ans] < '0'  || s[ans] > '9') ans--;
            for(int i = 0; i <= ans; i++) printf("%c", s[i]);
            printf("\n");
            }
        }
    }
    return 0;
}

E. Sasha and Array（抄的代码）

#include<cstdio>
using namespace std;
typedef long long LL;
const int N = 100010;
const int P = 1000000007;

struct Matrix {
    int n,m;
    LL c[3][3];
    Matrix() {
        for(int i=0; i<2; i++)for(int j=0; j<2; j++)c[i][j]=0;
        n=m=0;
        return;
    }
    Matrix operator * (const Matrix & a) const {
        Matrix b;
        b.n=n;
        b.m=a.m;
        for(int i=0; i<n; i++)
            for(int j=0; j<b.m; j++) {
                for(int k=0; k<m; k++)
                    b.c[i][j]=(b.c[i][j]+c[i][k]*a.c[k][j])%P;
            }
        return b;
    }
    Matrix operator + (const Matrix & a) const {
        Matrix b;
        b.n=n;
        b.m=m;
        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++)
                b.c[i][j]=(a.c[i][j]+c[i][j])%P;
        return b;
    }
} o,ini,oo,T[N<<2],tag[N<<2];

Matrix FP(Matrix a,int x) {
    oo=o;
    for(; x; x>>=1,oo=oo*oo)
        if(x&1) a=a*oo;
    return a;
}

int n,m,seq[N];

void Build(int x,int l,int r) {
    T[x].n=1,T[x].m=2;
    if(l==r) {
        tag[x].n=tag[x].m=0;
        T[x]=ini;
        T[x]=FP(T[x],seq[l]-1);
        return;
    }
    int mid=(l+r)>>1;
    Build(x<<1,l,mid);
    Build(x<<1|1,mid+1,r);
    T[x]=T[x<<1]+T[x<<1|1];
    return;
}

void Pushdown(int x) {
    if(tag[x].n==0) return;
    T[x<<1]=T[x<<1]*tag[x];
    if(tag[x<<1].n==0) tag[x<<1]=tag[x];
    else tag[x<<1]=tag[x<<1]*tag[x];
    T[x<<1|1]=T[x<<1|1]*tag[x];
    if(tag[x<<1|1].n==0) tag[x<<1|1]=tag[x];
    else tag[x<<1|1]=tag[x<<1|1]*tag[x];
    tag[x].n=tag[x].m=0;
    return;
}

void Change(int x,int l,int r,int L,int R,Matrix d) {
    if(L<=l&&r<=R) {
        if(tag[x].n==0) tag[x]=d;
        else tag[x]=tag[x]*d;
        T[x]=T[x]*d;
        return;
    }
    Pushdown(x);
    int mid=(l+r)>>1;
    if(L<=mid) Change(x<<1,l,mid,L,R,d);
    if(R>mid) Change(x<<1|1,mid+1,r,L,R,d);
    T[x]=T[x<<1]+T[x<<1|1];
    return;
}

LL Query(int x,int l,int r,int L,int R) {
    if(L<=l&&r<=R) return T[x].c[0][1];
    Pushdown(x);
    int mid=(l+r)>>1;
    LL res=0;
    if(L<=mid) res+=Query(x<<1,l,mid,L,R);
    if(R>mid) res+=Query(x<<1|1,mid+1,r,L,R);
    res%=P;
    return res;
}

int main() {
    ini.n=1;
    ini.m=2;
    ini.c[0][1]=1ll;
    o.n=2,o.m=2;
    o.c[1][0]=1ll;
    o.c[0][1]=1ll;
    o.c[1][1]=1ll;

    scanf("%d%d",&n,&m);
    for(int i=1; i<=n; i++) scanf("%d",&seq[i]);
    Build(1,1,n);

    int typ,l,r,x;
    for(int i=1; i<=m; i++) {
        scanf("%d%d%d",&typ,&l,&r);
        if(typ==2) printf("%I64d\n",Query(1,1,n,l,r));
        else {
            scanf("%d",&x);
            Change(1,1,n,l,r,FP(o,x-1));
        }
    }
    return 0;
}