SGU 220 Little Bishops(棋盘放象)

题目链接:http://acm.sgu.ru/problem.php?contest=0&problem=220

题意:在n*n的棋盘上放K个象,使得两两之间不互相攻击。有多少种放法?

思路:如下图所示,将棋盘染色,则在蓝色格子中放的象不可能攻击到红色格子,红色也一样。这样红蓝就能分开考虑。将棋盘翻转45度,这样就跟棋盘放车问题一样。

f[i][j]=f[i-1][j]+f[i-1][j-1]*(a[i]-(j-1))其中f[i][j]表示前i行放j个车的方案数,a[i]表示第i行的可放位置数。最后枚举在红色格子中放置的象的个数,剩下的象放在蓝色格子中。

SGU 220 Little Bishops(棋盘放象)_第1张图片

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


#define max(x,y) ((x)>(y)?(x):(y))
#define min(x,y) ((x)<(y)?(x):(y))
#define abs(x) ((x)>=0?(x):-(x))
#define i64 long long
#define u32 unsigned int
#define u64 unsigned long long
#define clr(x,y) memset(x,y,sizeof(x))
#define CLR(x) x.clear()
#define ph(x) push(x)
#define pb(x) push_back(x)
#define Len(x) x.length()
#define SZ(x) x.size()
#define PI acos(-1.0)
#define sqr(x) ((x)*(x))

#define FOR0(i,x) for(i=0;i=0;i--)
#define DOW1(i,x) for(i=x;i>=1;i--)
#define DOW(i,a,b) for(i=a;i>=b;i--)
using namespace std;


void RD(int &x){scanf("%d",&x);}
void RD(i64 &x){scanf("%I64d",&x);}
void RD(u32 &x){scanf("%u",&x);}
void RD(double &x){scanf("%lf",&x);}
void RD(int &x,int &y){scanf("%d%d",&x,&y);}
void RD(i64 &x,i64 &y){scanf("%I64d%I64d",&x,&y);}
void RD(u32 &x,u32 &y){scanf("%u%u",&x,&y);}
void RD(double &x,double &y){scanf("%lf%lf",&x,&y);}
void RD(int &x,int &y,int &z){scanf("%d%d%d",&x,&y,&z);}
void RD(i64 &x,i64 &y,i64 &z){scanf("%I64d%I64d%I64d",&x,&y,&z);}
void RD(u32 &x,u32 &y,u32 &z){scanf("%u%u%u",&x,&y,&z);}
void RD(double &x,double &y,double &z){scanf("%lf%lf%lf",&x,&y,&z);}
void RD(char &x){x=getchar();}
void RD(char *s){scanf("%s",s);}
void RD(string &s){cin>>s;}


void PR(int x) {printf("%d\n",x);}
void PR(i64 x) {printf("%I64d\n",x);}
void PR(u32 x) {printf("%u\n",x);}
void PR(double x) {printf("%.4lf\n",x);}
void PR(char x) {printf("%c\n",x);}
void PR(char *x) {printf("%s\n",x);}
void PR(string x) {cout<

  

转载于:https://www.cnblogs.com/jianglangcaijin/archive/2013/01/22/2872059.html

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