[Java]线段树

线段树

不含懒标记（单点修改）

代码

维护区间最大/最小值

Node[] tr = new Node[400010];
class Node{
    int l, r, max, min;
    Node(int l, int r, int max, int min){
        this.l = l;
        this.r = r;
        this.max = max;
        this.min = min;
    }
}

void build(int u, int l, int r){
    tr[u] = new Node(l, r, 0, 0x3f3f3f3f);
    if(l == r) return ;
    int mid = l + r >> 1;
    build(u << 1, l, mid);
    build(u << 1 | 1, mid + 1, r);
}

void pushup(int u){
    tr[u].max = Math.max(tr[u << 1].max, tr[u << 1 | 1].max);
    tr[u].min = Math.min(tr[u << 1].min, tr[u << 1 | 1].min);
}

int query1(int u, int l, int r){
    if(l <= tr[u].l && tr[u].r <= r) return tr[u].max;
    int mid = tr[u].l + tr[u].r >> 1, v = 0;
    if(l <= mid) v = query1(u << 1, l, r);
    if(r > mid) v = Math.max(v, query1(u << 1 | 1, l, r));
    return v;
}

int query2(int u, int l, int r){
    if(l <= tr[u].l && tr[u].r <= r) return tr[u].min;
    int mid = tr[u].l + tr[u].r >> 1, v = 0x3f3f3f3f;
    if(l <= mid) v = query2(u << 1, l, r);
    if(r > mid) v = Math.min(v, query2(u << 1 | 1, l, r));
    return v;
}

void update(int u, int x, int v){
    if(tr[u].l == x && tr[u].r == x) {
        tr[u].max = v;
        tr[u].min = v;
    }
    else{
        int mid = tr[u].l + tr[u].r >> 1;
        if(x <= mid) update(u << 1, x, v);
        else update(u << 1 | 1, x, v);
        pushup(u);
    }
}

含懒标记（区间修改）

代码

static Node[] tr = new Node[4 * N];
static class Node {
    int l, r;
    long sum, add;

    public Node(int l, int r, long sum, long add) {
        this.l = l;
        this.r = r;
        this.sum = sum;
        this.add = add;
    }
}

static void pushup(int u){
    tr[u].sum = tr[u << 1].sum + tr[u << 1 | 1].sum;
}

static void pushdown(int u){
    Node root = tr[u], left = tr[u << 1], right = tr[u << 1 | 1];
    if(root.add != 0){
        left.add += root.add;
        left.sum += (left.r - left.l + 1) * root.add;
        right.add += root.add;
        right.sum += (right.r - right.l + 1) * root.add;
        root.add = 0;
    }
}

static void build(int u, int l, int r){
    if(l == r) tr[u] = new Node(l, r, w[l], 0);
    else{
        tr[u] = new Node(l, r, 0, 0);
        int mid = l + r >> 1;
        build(u << 1, l, mid);
        build(u << 1 | 1, mid + 1, r);
        pushup(u);
    }
}

static void modify(int u, int l, int r, int d){
    if(tr[u].l >= l && tr[u].r <= r) {
        tr[u].add += d;
        tr[u].sum += (long) (tr[u].r - tr[u].l + 1) * d;
    }else {
        pushdown(u);
        int mid = tr[u].l + tr[u].r >> 1;
        if(l <= mid) modify(u << 1, l, r, d);
        if(r > mid) modify(u << 1 | 1, l, r, d);
        pushup(u);
    }
}

static long query(int u, int l, int r){
    if(tr[u].l >= l && tr[u].r <= r) return tr[u].sum;
    else{
        pushdown(u);
        int mid = tr[u].l + tr[u].r >> 1;
        long res = 0;
        if(l <= mid) res = query(u << 1, l, r);
        if(r > mid) res += query(u << 1 | 1, l, r);
        return res;
    }
}