SRM 564

呜呜呜呜呜，被虐爆了……

第一题就不知道怎么做，后来自己归纳了一下才发现象棋的规律，还因为写错了一个地方被challenge了，呜呜呜呜，我简直弱爆了。

第二题组合数学加动态规划，第三题估计也是动态规划，完全没有思路。。。。

我还是滚去好好学我的离散数学吧。。。。

 

division2的第三题真是好题，让我下午做了整整3个小时，最后卡时过了（标程应该也超时吧……）

分析可见http://apps.topcoder.com/wiki/display/tc/SRM+564，非常非常精彩，强烈推荐。

我的代码：

#include <vector>#include <list>#include <map>#include <set>#include <deque>#include <stack>#include <bitset>#include <algorithm>#include <functional>#include <numeric>#include <utility>#include <sstream>#include <iostream>#include <iomanip>#include <cstdio>#include <cmath>#include <cstdlib>#include <queue>#include <string.h>#include <ctime>using namespace std;class KnightCircuit {public:long long maxSize(int, int, int, int);int gcd(int a, int b);long long bfs(int w, int h, int a, int b);};//when the scale is very small, just use breath first searchlong long KnightCircuit::bfs(int w, int h, int a, int b){bool** check = new bool*[h+1];for(int i=0; i <= h; i++)check[i] = new bool[w+1];//mark the corresponding directionsint dir_x[]={a, a, -a, -a, b, b, -b, -b};int dir_y[]={b, -b, b, -b, a, -a, a, -a};long long goal=0;clock_t start=clock();for(int m=0; m<h; m++)for(int n=0; n<w; n++){clock_t end=clock();if((double)(end-start)/CLOCKS_PER_SEC > 1.0)return goal;for(int i=0; i<=h; i++)for(int j=0; j<=w; j++)check[i][j] = false;check[m][n] = true;queue<int> q;while(q.empty() == false)q.pop();q.push(m); q.push(n);long long res=1;while(q.empty() == false){int x = q.front();q.pop();int y = q.front();q.pop();//search for the next stepfor(int i=0; i<8; i++){int tmp_x = x + dir_x[i];int tmp_y = y + dir_y[i];if(tmp_x < 0 || tmp_y < 0 || tmp_x >= h || tmp_y >= w)continue;if(check[tmp_x][tmp_y] == false){check[tmp_x][tmp_y] = true;q.push(tmp_x);q.push(tmp_y);res++;}//end if}//end for loop}//end while loopgoal=max(goal, res);}return goal;}//end method bfs//hunt for the greatest common divisor using Euclid methodint KnightCircuit::gcd(int a, int b){    while(a > 0){int c = a;a = b % a;b = c;        }    return b;}long long KnightCircuit::maxSize(int w, int h, int a, int b) {int g = gcd(a, b);//minimize the scale of problemif( g != 1)return maxSize((1 + (w - 1)/g), (1 + (h - 1)/g), a/g, b/g);//just use breath first searchif((w <= 20) || (h <= 20))return bfs(w, h, a, b);//all positions are reachableif((a + b) % 2 == 1)return w * (long long)h;//only half positions are reachableelsereturn (1 + (long long)w * h)/2;}////Powered by [KawigiEdit] 2.0!