func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e6;   int L[N], R[N], sp[N], levsp[30], lev[N];   long long val[N], a[N];   void lazyUpdate(int node) {     if (!L[node]) return;     if (sp[node] ^ levsp[lev[node]]) {       swap(L[node], R[node]);       sp[node] ^= 1;     }   }   long long build(int node, int l, int r, int lv) {     if (l == r) return val[node] = a[l];     int mid = l + r >> 1;     lev[node] = lv;     L[node] = node << 1, R[node] = node << 1 | 1;     val[node] =         build(L[node], l, mid, lv - 1) + build(R[node], mid + 1, r, lv - 1);     return val[node];   }   long long update(int node, int l, int r, int pos, int k) {     lazyUpdate(node);     if (r < pos || l > pos) return val[node];     if (l == r) return val[node] = k;     int mid = l + r >> 1;     return val[node] = update(L[node], l, mid, pos, k) +                        update(R[node], mid + 1, r, pos, k);   }   long long query(int node, int l, int r, int pos) {     lazyUpdate(node);     if (l > pos) return 0;     if (r <= pos) return val[node];     int mid = l + r >> 1;     return query(L[node], l, mid, pos) + query(R[node], mid + 1, r, pos);   }   int main() {     int n, q;     scanf( %d%d , &n, &q);     int nn = 1 << n;     for (int i = 1; i <= nn; i++) scanf( %lld , &a[i]);     build(1, 1, nn, n);     while (q--) {       int t, x, k;       scanf( %d , &t);       if (t == 1) {         scanf( %d%d , &x, &k);         update(1, 1, nn, x, k);       } else if (t == 2) {         scanf( %d , &k);         for (int i = 0; i <= k; i++) levsp[i] ^= 1;       } else if (t == 3) {         scanf( %d , &k);         levsp[k + 1] ^= 1;       } else {         int l, r;         scanf( %d%d , &l, &r);         printf( %lld n , query(1, 1, nn, r) - query(1, 1, nn, l - 1));       }     }     return 0;   }   