POJ 3468 A Simple Problem with Integers (线段树区间更新)

题目链接：

题目大意：

样例解释：

解题思路：

//Author LJH
//www.cnblogs.com/tenlee
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#define clc(a, b) memset(a, b, sizeof(a))
#define LL long long
using namespace std;

const int inf = 0x3f;
const int INF = 0x3f3f3f3f;
const int maxn = 1e5+5;

struct Node
{
int l, r;
LL sum, add;
}tree[maxn * 6];

void Build(int i, int l, int r);
void Update(int i, int l, int r, int val);
void PushDown(int i);
LL Query(int i, int l, int r);

int main()
{
int n, q;
int a, b, c;
char op;
while(~scanf("%d %d", &n, &q))
{
Build(1, 1, n);
while(q--)
{
scanf(" %c", &op);
if(op == 'Q')
{
scanf("%d %d", &a, &b);
printf("%lld\n", Query(1, a, b));
}
else
{
scanf("%d %d %d", &a, &b, &c);
Update(1, a, b, c);
}
}
}
return 0;
}

void Build(int i, int l, int r)
{
tree[i].l = l;
tree[i].r = r;
tree[i].add = 0;
if(l == r)
{
scanf("%lld", &tree[i].sum);
return;
}
int mid = (l + r) >> 1;
Build(i << 1, l, mid);
Build(i << 1 | 1, mid + 1, r);
tree[i].sum = tree[i<<1].sum + tree[i<<1|1].sum;
}

void Update(int i, int l, int r, int val)
{
if(tree[i].l == l && tree[i].r == r) //刚好满足时,就标记了
{
tree[i].add += val;
return;
}
tree[i].sum += (r - l + 1) * val; //注意此处是 r - l + 1, 而不是 tree[i].r - tree[i].l + 1
int mid = (tree[i].l + tree[i].r) >> 1;
if(r <= mid)
{
Update(i<<1, l, r, val);
}
else if(l > mid)
{
Update(i<<1|1, l, r, val);
}
else
{
Update(i<<1, l, mid, val);
Update(i<<1|1, mid+1, r, val);
}
}

void PushDown(int i)
{
tree[i<<1|1].add += tree[i].add;
tree[i<<1].add += tree[i].add;
tree[i].sum += (tree[i].r  - tree[i].l + 1) * tree[i].add;
tree[i].add = 0; //重置为0

}

LL Query(int i, int l, int r)
{
if(tree[i].add != 0)  // 向下更新
{
PushDown(i);
}
if(tree[i].l == l && tree[i].r == r)
{
return tree[i].sum;
}
int mid = (tree[i].l + tree[i].r) >> 1;
if(r <= mid)
{
return Query(i<<1, l, r);
}
else if(l > mid)
{
return Query(i<<1|1, l, r);
}
else
{
return (Query(i<<1, l, mid) + Query(i<<1|1, mid+1, r));
}

}