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这个要知道一个公式；
可以算是一道数学题吧。如果知道皮克定理就行了。皮克定理说明了其面积S和内部格点数目a、边上格点数目b的关系：S = a + b/2 - 1。
根据三角形面积公式求出S。如果知道了b，那么三角形内部格点数目a也就求出来了。
可以证明，一条直线((0,0),(n,m))上的格点数等于n与m的最大公约数+1。
即b=gcd(n,m)+1. gcd(n,m)为n与m的最大公约数。
/* ID: qq104801 LANG: C++ TASK: fence9 */ #include <iostream> #include <fstream> #include <cstring> #include <vector> #include <queue> #include <stack> #include <algorithm> using namespace std; #define nmax 27 int gcd(int a,int b) { return b==0?a:gcd(b,a%b); } void test() { freopen("fence9.in","r",stdin); freopen("fence9.out","w",stdout); int n,m,p,b=0,s; cin>>n>>m>>p; s=(m*p)/2; b+=gcd(n,m); if(n!=p)b+=gcd(abs(n-p),m); else b+=m; b+=p; cout<<s+1-(b/2)<<endl; } int main () { test(); return 0; }
test data:
USACO Training Grader Results 26 users online ARE/1 BGD/1 CHN/8 DNK/1 EGY/1 GEO/2 IND/2 IRN/1 ISR/2 MAC/1 MYS/1 TWN/1 USA/4 USER: cn tom [qq104801] TASK: fence9 LANG: C++ Compiling... Compile: OK Executing... Test 1: TEST OK [0.003 secs, 3372 KB] Test 2: TEST OK [0.005 secs, 3372 KB] Test 3: TEST OK [0.005 secs, 3372 KB] Test 4: TEST OK [0.008 secs, 3372 KB] Test 5: TEST OK [0.008 secs, 3372 KB] Test 6: TEST OK [0.008 secs, 3372 KB] Test 7: TEST OK [0.008 secs, 3372 KB] Test 8: TEST OK [0.008 secs, 3372 KB] Test 9: TEST OK [0.005 secs, 3372 KB] Test 10: TEST OK [0.008 secs, 3372 KB] Test 11: TEST OK [0.005 secs, 3372 KB] Test 12: TEST OK [0.005 secs, 3372 KB] All tests OK. YOUR PROGRAM (‘fence9‘) WORKED FIRST TIME! That‘s fantastic -- and a rare thing. Please accept these special automated congratulations. Here are the test data inputs: ------- test 1 ---- 1 1 2 ------- test 2 ---- 2 2 4 ------- test 3 ---- 10 20 10 ------- test 4 ---- 0 100 100 ------- test 5 ---- 0 200 20000 ------- test 6 ---- 100 200 50 ------- test 7 ---- 10000 100 10 ------- test 8 ---- 0 20000 2 ------- test 9 ---- 200 30000 30000 ------- test 10 ---- 30000 30000 30001 ------- test 11 ---- 15000 100 30000 ------- test 12 ---- 0 31999 31999 Keep up the good work! Thanks for your submission!
标签：style blog http color io os ar for div
原文地址：http://www.cnblogs.com/dpblue/p/3975900.html
