Revise paste 5d548278f73da

#include <iostream>
#include <map>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 1e5 + 10;
const int INF = 2e9;
int n, a[maxn];
pair<int, int> segment_tree[3 * maxn];

pair<int, int> merge_nodes(pair<int, int> A, pair<int, int> B) {
    vector<int> v{A.first, A.second, B.first, B.second};
    sort(v.begin(), v.end());
    
    return {v[2], v[3]};
}
void build_tree(int L, int R, int node) {
    if(L == R) {
        segment_tree[node] = {a[L], -INF};
    }
    else {
        int middle = (L + R) / 2;
        build_tree(L, middle, 2 * node);
        build_tree(middle + 1, R, 2 * node + 1);
        segment_tree[node] = merge_nodes(segment_tree[2 * node], segment_tree[2 * node + 1]);
    }
}

pair<int, int> query(int i, int j, int L, int R, int node) {
    if(i <= L and R <= j) {
        return segment_tree[node];
    }
    if(R < i or j < L) {
        return {-INF, -INF};
    }
    
    int middle = (L + R) / 2;
    pair<int, int> left_side = query(i, j, L, middle, 2 * node);
    pair<int, int> right_side = query(i, j, middle + 1, R, 2 * node + 1);
    
    return merge_nodes(left_side, right_side);
}

void update(int idx, int new_val, int L, int R, int node) {
    if(L == R) {
        segment_tree[node] = {new_val, -INF};
        return;
    }
    int middle = (L + R) / 2;
    if(idx <= middle) {
        update(idx, new_val, L, middle, 2 * node);
    }
    else {
        update(idx, new_val, middle + 1, R, 2 * node + 1);
    }
    segment_tree[node] = merge_nodes(segment_tree[2 * node], segment_tree[2 * node + 1]);
    
}

int main() {
    ios_base::sync_with_stdio(false);
    cin >> n;
    
    for(int i = 0; i < n; i++) {
        cin >> a[i];
    }
    
    
    build_tree(0, n - 1, 1);
    
    int q;
    cin >> q;
    
    for(int i = 0; i < q; i++) {
        char c;
        cin >> c;
        
        if(c == 'Q') {
            int x, y;
            cin >> x >> y;
            
            pair<int, int> res = query(x - 1, y - 1, 0, n - 1, 1);
            cout << res.first + res.second << endl;
        }
        else {
            int idx, val;
            cin >> idx >> val;
            
            update(idx - 1, val, 0, n - 1, 1);
        }
    }
    return 0;
}