线段树:POJ3468-A Simple Problem with Integers(线段树注意事项)
2017-07-28 09:55
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A Simple Problem with Integers
Time Limit: 10000MSMemory Limit: 65536K
Description
You have N integers, A1, A2, … , AN. You need to deal with two kinds of operations. One type of operation is to add some given number to each number in a given interval. The other is to ask for the sum of numbers in a given interval.Input
The first line contains two numbers N and Q. 1 ≤ N,Q ≤ 100000.The second line contains N numbers, the initial values of A1, A2, … , AN. -1000000000 ≤ Ai ≤ 1000000000.
Each of the next Q lines represents an operation.
“C a b c” means adding c to each of Aa, Aa+1, … , Ab. -10000 ≤ c ≤ 10000.
“Q a b” means querying the sum of Aa, Aa+1, … , Ab.
Output
You need to answer all Q commands in order. One answer in a line.Sample Input
10 51 2 3 4 5 6 7 8 9 10
Q 4 4
Q 1 10
Q 2 4
C 3 6 3
Q 2 4
Sample Output
455
9
15
Hint
The sums may exceed the range of 32-bit integers.解题心得:
这是一个最简单的线段树,题意就是给你一系列数,每次询问l到r的和或者每次在l到r之间的每一个数加上一个数。很简单啊,但是万万没想到比赛居然崩在这个题上面,将r和R传参的时候写反了,tm样例和所有自己造的数据都过了,哎,已砍手。google翻译还吧这题翻译成了神题,我去。
这个题还是很有教训的,线段树的代码比较麻烦,要不停的向上维护,向下传递,不停的传递参数,所以在写的时候一定要注意,写慢一点,不然线段树出现了bug很难找,思路不复杂别死在了手贱上面。线段树的lazy标记的时候一定要记得下移,以及在每次递归之后记得向上维护,向上维护的时候一定要注意父节点和两个子节点的关系,该传递一些什么,别和lazy下移的时候搞混了。
#include<cstring> #include<stdio.h> #include<string> #include<queue> #include<algorithm> #include<stack> #include<math.h> using namespace std; const int maxn = 1e6+100; struct node { long long l,r,sum,lazy; }tree[maxn<<2]; void pushup(long long root) { tree[root].sum = tree[root<<1].sum + tree[root<<1|1].sum; } void pushdown(long long root) { if(tree[root].lazy == 0) return ; tree[root<<1].lazy += tree[root].lazy; tree[root<<1|1].lazy += tree[root].lazy; tree[root<<1].sum += (tree[root<<1].r - tree[root<<1].l + 1)*tree[root].lazy; tree[root<<1|1].sum += (tree[root<<1|1].r - tree[root<<1|1].l + 1)*tree[root].lazy; tree[root].lazy = 0; } void buildtree(long long l,long long r,long long root) { tree[root].l = l; tree[root].r = r; tree[root].lazy = 0; if(l == r) { scanf("%lld",&tree[root].sum); return ; } long long mid = (l + r) >> 1; buildtree(l,mid,root<<1); buildtree(mid+1,r,root<<1|1); pushup(root); } long long query(long long L,long long R,long long l,long long r,long long root) { if(l == L && R ==r) { return tree[root].sum; } long long mid = (l + r)>>1; pushdown(root); if(R <= mid) { return query(L,R,l,mid,root<<1); } else if(L > mid) { return query(L,R,mid+1,r,root<<1|1); } else return query(mid+1,R,mid+1,r,root<<1|1)+ query(L,mid,l,mid,root<<1);//这里手贱找了一个小时的bug pushup(root); } void add(long long L,long long R,long long l,long long r,long long root,long long h) { if(l == L && R ==r) { tree[root].lazy += h; tree[root].sum += (r - l +1)*h; return; } pushdown(root); long long mid = (l + r) >> 1; if(R <= mid) add(L,R,l,mid,root<<1,h); else if(L > mid) add(L,R,mid+1,r,root<<1|1,h); else { add(L,mid,l,mid,root<<1,h); add(mid+1,R,mid+1,r,root<<1|1,h); } pushup(root); } int main() { long long n,m; while(scanf("%lld%lld",&n,&m) != EOF) { long long sum = 0; buildtree(1,n,1); while(m--) { long long a,b,h; char c[10];//尽量别输入%c,容易挂掉,%s挺好的 scanf("%s",&c);//这里也要注意一下输入的问题,不同的字符对应的不同个数的int输入 if(c[0] == 'C') { long long h; scanf("%lld%lld%lld",&a,&b,&h); add(a,b,1,n,1,h); } else if(c[0] == 'Q') { scanf("%lld%lld",&a,&b); sum = query(a,b,1,n,1); printf("%lld\n",sum); } } } return 0; }
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