分块算法

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;
 
using LL = long long;
LL getint();
int N, M;
LL block, val[500005], blg[500005], tag[1005];
void add(int l, int r, int key);
 
int main(){
  N = getint(), block = sqrt(N);
  int i;
  for(i = 1; i <= N; i++)
    val[i] = getint();
  for(i = 1; i <= N; i++)
    blg[i] = (i - 1) / block + 1;
  for(i = 1; i <= N; i++){
    int op, x, y, key;
    op = getint(), x = getint();
    y = getint(), key = getint();
    if(op == 0){
      add(x, y, key);
    }else
      printf("%lld\n", val[y] + tag[blg[y]]);
  }
  return 0;
}
 
void add(int l, int r, int key){
  int i, top;
  for(i = l, top = min(blg[l] * block, 1LL * r); i <= top; i++)
    val[i] += key;
  if(blg[l] != blg[r])
    for(i = (blg[r] - 1) * block + 1; i <= r; i++)
      val[i] += key;
  for(i = blg[l] + 1; i <= blg[r] - 1; i++)
    tag[i] += key;
}
 
LL getint(){
  LL res = 0, mark = 1;
  char ch = getchar();
  while(ch<‘0‘ || ch>‘9‘){
    if(ch == ‘-‘) mark = -1;
    ch = getchar();
  }
  while(ch >= ‘0‘ && ch <= ‘9‘)
    res = 10 * res + ch - ‘0‘, ch = getchar();
  return mark * res;
}