版权声明:https://blog.csdn.net/qq_41730082 https://blog.csdn.net/qq_41730082/article/details/86409768
题目链接
一道线段树的区间更新,相等即剪枝优化的题(中间竟然忘记了lazy标记的传递,害得我WA了一次……)。
题意:有1~N的一串元素,每个数的初始颜色是他的序号,每次可以改变一串元素的颜色为X,但是同时,每个串的颜色都会变成X,并且每个点会有一个增量原a[i] - X的绝对值,然后,对于每个增量,我们求区间和的时候,就是求区间的增量。
既然是区间附等值,不如就直接判断是不是等值即可,等值的查询内的区间就直接改变就是了。
#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
#define INF 0x3f3f3f3f
#define HalF (l + r)>>1
#define ls rt<<1
#define rs rt<<1|1
#define Lson ls, l, mid
#define Rson rs, mid+1, r
#define QL Lson, ql, qr
#define QR Rson, ql, qr
#define myself rt, l, r
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int maxN = 1e5 + 7;
int N, M;
ll tree[maxN<<2], sum[maxN<<2], lazy[maxN<<2];
inline void pushup(int rt)
{
if(tree[ls] == tree[rs]) tree[rt] = tree[ls];
else tree[rt] = 0;
sum[rt] = sum[ls] + sum[rs];
}
inline void buildTree(int rt, int l, int r)
{
sum[rt] = lazy[rt] = 0;
if(l == r)
{
tree[rt] = l;
return;
}
int mid = HalF;
buildTree(Lson);
buildTree(Rson);
pushup(rt);
}
inline void pushdown(int rt, int l, int r)
{
if(tree[rt]) tree[ls] = tree[rs] = tree[rt];
if(lazy[rt])
{
int mid = HalF;
sum[ls] += lazy[rt] * (mid - l + 1);
sum[rs] += lazy[rt] * (r - mid);
lazy[ls] += lazy[rt];
lazy[rs] += lazy[rt];
lazy[rt] = 0;
}
}
inline void update(int rt, int l, int r, int ql, int qr, ll val)
{
if(ql<=l && qr>=r && tree[rt])
{
sum[rt] += abs(val - tree[rt]) * (r - l + 1);
lazy[rt] += abs(val - tree[rt]);
tree[rt] = val;
return;
}
pushdown(myself);
int mid = HalF;
if(ql > mid) update(QR, val);
else if(qr <= mid) update(QL, val);
else { update(QL, val); update(QR, val); }
pushup(rt);
}
inline ll query(int rt, int l, int r, int ql, int qr)
{
if(ql<=l && qr>=r) return sum[rt];
pushdown(myself);
int mid = HalF;
if(ql > mid) return query(QR);
else if(qr <= mid) return query(QL);
else return query(QL) + query(QR);
}
int main()
{
scanf("%d%d", &N, &M);
buildTree(1, 1, N);
while(M--)
{
int op, x, y;
scanf("%d%d%d", &op, &x, &y);
if(op == 1)
{
ll val; scanf("%lld", &val);
update(1, 1, N, x, y, val);
}
else
{
printf("%lld\n", query(1, 1, N, x, y));
}
}
return 0;
}