【不定期更新】noip复习(或许有误请指正)

void find(int l,int r){
    if (l>r || a[l]>x || a[r]<x) return;
    int mid = (l+r) >> 1;
    if (a[mid] == x){
        if (mid < pos)pos=mid;
        if (a[mid-1] == x) find(l, mid-1);
        if (a[mid+1] == x) find(mid+1, r);
        return;
    }
    if (x > a[mid]) find(mid+1, r);
    else find(l, mid-1);
}

bool is_prime(int x){
    if (x <= 1) return 0;
    for (int i = 2; i <= floor(sqrt(x)+0.5); i++){
        if (x % i == 0) return 0;
    }
    return 1;
}

for (int i = 1; i <= n; i++){
    if (!flag[i]) ans[tot++]=i;
    for (int j=0 ; j < tot && i*ans[j] <= n ;j++){
        flag[i * ans[j]]=1;
        if (i % ans[j]==0) break;
    }
}

void merge(int a, int m, int b, int n){
    int i = a, j = b, k = a;
    while (i <= m && j <= n){
        if (s[i] <= s[j]) t[k++] = s[i++];
        else{
            t[k++] = s[j++];
            ans += m-i+1;
        }
    }
    while (i <= m) t[k++] = s[i++];
    while (j <= n) t[k++] = s[j++];
    for (int i=a; i<=n; i++) s[i] = t[i];
}
void mergesort(int a, int b){
    if (a == b) return;
    int mid = (a+b) / 2;
    mergesort(a, mid);
    mergesort(mid+1, b);
    merge(a, mid, mid+1, b);
}
//ans为逆序对个数

void shift_down(int p){
    int mp = 2*p;
    while (mp <= n){
        if (p*2 == n || a[p*2] < a[p*2+1]) mp=2*p; else mp=2*p+1;
        if (a[mp] < a[p]) swap(a[mp], a[p]); else break;
        p=mp; mp=2*p;
    }
}

void shift_up(int p){
    while (p > 1 && a[p] < a[p/2]){
        swap(a[p], a[p/2]);
        p /= 2;
    }
}

int find(int x){return (x==f[x]) ? x : f[x] = find(f[x]); }
int union(int a, int b){
    int x=find(a), y=find(b);
    if (rank[a]<rank[b]) father[a]=b;
    else{
        father[b]=a; if (rank[b]==rank[a])++rank[b];
    }
}

struct node{int l, r, cover; };
void bulid_tree(int p, int s, int t){
    node &a=tree[p];
    a.l = s; a.r = t;
    if (a.l == a.r) return;
    int mid = (s+t) >> 1;
    bulid_tree(p*2, s, mid);
    bulid_tree(p*2+1, mid+1, t);
}
void insert(int p, int s, int t){
    node &a = tree[p];
    if (a.l == s && a.r == t) {a.cover++; return;}
    if (a.l == a.r) return; //不能写成s==t
    int mid = (a.l+a.r) >> 1;
    if (t <= mid) insert(p*2, s, t);
    else if (s > mid) insert(p*2+1, s, t);
    else{
        insert(p*2, s, mid);
        insert(p*2+1, mid+1, t);
    }
}
 
int count(int p, int x){
    node &a = tree[p];
    if (a.l == x && a.r == x) return a.cover;
    int mid = (a.l+a.r) >> 1,t = 0;
    if (x <= mid) t = count(p*2, x);
    else t = count(p*2+1, x);
    return (a.cover + t);
}

#define lowbit(i) i&(-i)
void update(int x, int y, int d){
    x++; y++;
    for (int i=x; i<INF; i+=lowbit(i))
        for (int j=y; j<INF; j += lowbit(j))
        c[i][j] += d;
}
 
int count(int x,int y){
    int ans=0;
    x++; y++;
    for (int i=x;i;i-=lowbit(i))
        for (int j=y;j;j-=lowbit(j))
        ans+=c[i][j];
    return ans;
} 

struct Trie{
    int tot,root,child[max_node][charset];
    bool flag[max_node];
    Trie()
    {
        memset(child[1],0,sizeof(child[1]));
        flag[1]=0;
        root=tot=1;
    }
void insert(const char *str) //刚传进来的时候*str表示的是str[0] str表示整个字符数组
    {
        int *cur=&root;
        for (const char *p=str;*p;++p) //p刚开始指向str[0] ++p表示取str的下一位 若为‘\0‘则退出
        {
            cur=&child[*cur][*p-‘a‘];
            if (*cur==0)
            {
                *cur=++tot;
                memset(child[tot],0,sizeof(child[tot]));
                flag[tot]=0;
            }
        }
        flag[*cur]=1;
    }
    bool query(const char *str)
    {
        int *cur=&root;
        for (const char *p=str;*p && *cur;++p)
            cur=&child[*cur][*p-‘a‘];
        return (*cur && flag[*cur]);
    }
};