线段树——＞建树build,区间查询query,单点更新adddate,区间更新update,懒标记

cpp 复制代码

void build(int node, int start, int end) {
    if(start == end) {
        tree[node] = arr[start];
    } else {
        int mid = (start + end) / 2;
        build(2 * node, start, mid);
        build(2 * node + 1, mid + 1, end);
        tree[node] = tree[2 * node] + tree[2 * node + 1];
    }
}

cpp 复制代码

int query(int node, int start, int end, int l, int r) {
    updatelazy(node, start, end); // 确保本节点的值是最新的
    if (r < start || l > end) return 0; // 当前区间与查询区间无交集
    if (l <= start && end <= r) return tree[node]; // 当前区间完全包含在查询区间内

    int mid = (start + end) / 2;
    return query(2 * node, start, mid, l, r) + query(2 * node + 1, mid + 1, end, l, r);
}

cpp 复制代码

void adddate(int node, int start, int end, int index, int val) {
    if(start == end) {
        arr[index] = val;
        tree[node] = val;
    } else {
        int mid = (start + end) / 2;
        if(index >= start && index <= mid) {
            adddate(2 * node, start, mid, index, val);
        } else {
            adddate(2 * node + 1, mid + 1, end, index, val);
        }
        tree[node] = tree[2 * node] + tree[2 * node + 1];
    }
}

cpp 复制代码

void update(int node, int start, int end, int l, int r, int val) {
    updatelazy(node, start, end); // 处理本节点的懒标记
    if (r < start || l > end) return; // 当前区间与更新区间无交集

    if (l <= start && end <= r) {
        tree[node] += (end - start + 1) * val;
        if (start != end) {
            lazy[2 * node] += val;
            lazy[2 * node + 1] += val;
        }
        return;
    }

    int mid = (start + end) / 2;
    update(2 * node, start, mid, l, r, val);
    update(2 * node + 1, mid + 1, end, l, r, val);
    tree[node] = tree[2 * node] + tree[2 * node + 1];
}

cpp 复制代码

void updatelazy(int node, int start, int end) {
    if (lazy[node] != 0) {
        // 更新当前区间的和，lazy[node]是需要加的值
        tree[node] += (end - start + 1) * lazy[node];
        if (start != end) {
            // 将懒标记传递给子节点
            lazy[2 * node] += lazy[node];
            lazy[2 * node + 1] += lazy[node];
        }
        // 清除当前节点的懒标记
        lazy[node] = 0;
    }
}

cpp 复制代码

int main() {
    int n, m;
    cin >> n >> m;

    for(int i = 1; i <= n; i++) {
        cin >> arr[i];
    }
    build(1, 1, n);

    for(int i = 0; i < m; i++) {
        char s;
        int x, y, z;
        cin >> s;
        if (s == 'Q') {
            cin >> x >> y;
            cout << query(1, 1, n, x, y) << endl;
        } else if (s == 'C') {
            cin >> x >> y >> z;
            update(1, 1, n, x, y, z);
        } else if (s == 'D') {
            cin >> x >> y;
            adddate(1, 1, n, x, y);
        }
    }

    return 0;
}