Gerald and Giant Chess Problem's Link: http://codeforces.com/contest/559/problem/C Mean: 一个n*m的网格,让你从左上角走到右下角,有一些点不能经过,问你有多少种方法. analyse: BZOJ上的原题. 首先把坏点和终点以x坐标为第一键值,y坐标为第二键值排序 . 令fi表示从原点不经过任何坏点走到第i个点的个数,那么有DP方程: fi=Cxixi+yi−∑(xj<=xi,yj<=yi)C(xi−xj)…

C. Gerald and Giant Chess Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/559/problem/C Description Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to . The…

题目链接:http://codeforces.com/contest/560/problem/E 给你一个n*m的网格,有k个坏点,问你从(1,1)到(n,m)不经过坏点有多少条路径. 先把这些坏点排序一下. dp[i]表示从(1,1)到第i个坏点且不经过其他坏点的路径数目. dp[i] = Lucas(x[i], y[i]) - sum(dp[j]*Lucas(x[i]-x[j], y[i]-x[j])) , x[j] <= x[i] && y[j] <= y[i] //到i…

这场CF又掉分了... 这题题意大概就给一个h*w的棋盘,中间有一些黑格子不能走,问只能向右或者向下走的情况下,从左上到右下有多少种方案. 开个sum数组,sum[i]表示走到第i个黑点但是不经过其他黑点的方案数. 式子是sum[i]=c(x[i]+y[i],x[i])-Σ(sum[j]*c(x[i]-x[j]+y[i]-y[j],x[i]-x[j])). c(x+y,x)表示从格子(1,1)到(x,y)的方案数(没有黑点). 因此每个点按x[i]+y[i]的值排个序,然后n^2弄一下他们的拓扑…

Gerald's Hexagon Problem's Link: http://codeforces.com/contest/559/problem/A Mean: 按顺时针顺序给出一个六边形的各边长(且保证每个内角都是120度),求能够分解成多少个边长为1的小正三角形. analyse: 由于每个内角都是120度,那么把三条边延长相交,一定能够得到一个正三角形. 求出正三角形的面积S1和补上的小三角形的面积S2,则answer=S1-S2. 这里不是真正意义上求正三角形的面积,而是直接求内部可…

C. Gerald's Hexagon Time Limit: 2 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/559/problem/A Description Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to . Then he me…

A. Gerald's Hexagon Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/559/problem/A Description Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to . Then he m…

B. Gerald is into Art Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/560/problem/B Description Gerald bought two very rare paintings at the Sotheby's auction and he now wants to hang them on the wall. For that he bought a…

[CF简单介绍] 提交链接:http://codeforces.com/contest/560/problem/C 题面: C. Gerald's Hexagon time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Gerald got a very curious hexagon for his birthday. The bo…

C. Gerald's Hexagon time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to .…