[Ideas] POJ 3663 Costume Party

Test instructions

Give the number of N, and M, ask the number of N to choose two numbers x, y to make the method of x+y<=m how many kinds, xy order independent.

Ideas:

Preprocessing all the numbers, the default x<y to enumerate.

For an x, the y that satisfies the condition must be within the [x,m-y] range. Even if there are many numbers.

Then count the equal cases separately.

Code:

#include "cstdlib" #include "Cstdio" #include "CString" #include "Cmath" #include "queue" #include "algorithm" #include " iostream "#include" map "using namespace std; #define LL __int64int V[1000002],a[25448];int Main () {    int n,s;    while (scanf ("%d%d", &n,&s)!=-1)    {        memset (v,0,sizeof (v));        for (int i=0;i<n;i++)        {            int x;            scanf ("%d", &x);            a[i]=x;            v[x]++;        }        for (int i=0;i<=1000000;i++) v[i]+=v[i-1];        Sort (a,a+n);        int ans=0;        for (int i=0;i<n;i++)        {            if (A[I]>=S/2) break;            Ans+=v[s-a[i]]-v[a[i]];        }        for (int i=1;i<=1000000;i++)        {            int tep=v[i]-v[i-1];            if (I>S/2) break;            if (!tep) continue;            ans+=tep* (tep-1)/2;        }        printf ("%d\n", ans);    }    return 0;}

[Ideas] poj 3663 Costume Party