POJ 2352 && HDU 1541 Stars (tree-like array)

At first thought, the total feeling is DP, but finally did not think of anything. And a violent hand.

Then start writing the line segment tree and the result is timed out. Feel a problem with the way your line tree is written. I'll write it sometime. Let's put the tree-like array in the first place.

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The tree array does not understand to see Rujia's Great White Book, that picture is very clear.

The main idea: the coordinates of the stars are given in the order of Y increments, and the points at the lower left of the dots represent the levels of this point, and how many 0~n-1 are asked? In fact, y is practically wooden.

Title Link: http://poj.org/problem?id=2352

http://acm.hdu.edu.cn/showproblem.php?pid=1541

The idea of a tree array is that every inquiry is the equivalent of asking how many points there are between 1~x (including x). Then we will read it and update it as well.

#include <cstdio> #include <cstring> #include <algorithm> #define N 32000+10using namespace Std;int a[n ],ans[n>>1];int lowbit (int x) {    return x& (-X);} int Sum (int x) {    int tot=0;    while (x>0)    {        tot+=a[x];        X-=lowbit (x);    }    return tot;} void update (int x,int v) {    while (x<=n)    {        a[x]+=v;        X+=lowbit (x);    }} int main () {    int n;    while (scanf ("%d", &n)!=eof)    {        int x, y;        memset (A,0,sizeof (a));        memset (ans,0,sizeof (ans));        for (int i=0;i<n;i++)        {            scanf ("%d%d", &x,&y);            x + +;    The range of 1~x.            ans[Sum (x)]++;            Update (x,1);  Update with A.        }        for (int i=0;i<n;i++)            printf ("%d\n", Ans[i]);    }    return 0;}

POJ 2352 && HDU 1541 Stars (tree-like array)