主席树模板

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;

const int M = 50006;
int w[M], a[M], root[M];
struct Tree{
    int ls, rs, w;
} tr[M << 4] ;

int tot ;

void insert(int &x, int l, int r, int d){
    tr[++tot] = tr[x];
    tr[tot].w ++;
    x = tot;
    if(l == r) return ;
    int m = (l+r) >> 1; 
    if(d <= m) insert(tr[tot].ls, l, m, d);
    else insert(tr[tot].rs, m+1, r, d);
}
int query(int rt, int R, int l, int r){
    if(l == r) return tr[rt].w;
    if(R >= r) return tr[rt].w;
    int m = (l + r) >> 1;
    int ret = 0;
    if(m <= R) ret += query(tr[rt].ls, R, l, m);
    if(R > m) ret += query(tr[rt].rs, R, m+1, r);
    return ret;
}

int main(){
    int T;
    scanf("%d", &T);
    int m, n, l, r, b;
    while(T -- ){
        scanf("%d%d", &n, &m);
        int tt = 0;
        for(int i = 1; i <= n; i ++){
            scanf("%d", a[i]);
            w[tt ++] = a[i];
        }
        sort(w, w+tt);
        int u = unique(w, w+tt) - w;
        root[0] = 0;
        for(int i = 1; i <= n; i ++){
            int d = lower_bound(w, w+u, a[i]) - w;
            root[i] = root[i-1];
            insert(root[i], 0, u-1, d);
        }
        while(m --){
            scanf("%d%d%d%d", &l, &r, &a, &b);
            int rr = lower_bound(w, w+u, b) - w;
            int ll = lower_bound(w, w+u, a+1) - w - 1;
            int ans = query(root[r], rr, 0, u-1) - query(root[l-1], ll, 0, u-1);
        }
    }
    return 0;
}

　　忘记是哪里的题目了~~就是个主席树的模板，保存一下。。。