UVa 1393 (容斥原理、GCD) Highways

#include <cstdio>
#include <algorithm>

const int maxn = 300;
int dp[maxn+1][maxn+1], ans[maxn+1][maxn+1];

int gcd(int a, int b)
{
return b == 0 ? a : gcd(b, a%b);
}

void Init()
{
for(int i = 1; i <= maxn; ++i)
for(int j = 1; j <= i; ++j)
{
if(i == j) dp[i][j] = dp[i][j-1] * 2 - dp[i-1][j-1] + (gcd(i, j) == 1);
else dp[i][j] = dp[i-1][j] + dp[i][j-1] - dp[i-1][j-1] + (gcd(i, j) == 1);
}

for(int i = 1; i <= maxn; ++i)
for(int j = 1; j <= i; ++j)
{
if(i == j) ans[i][j] = ans[i][j-1] * 2 - ans[i-1][j-1] + dp[i][j] - dp[i/2][j/2];
else ans[i][j] = ans[i][j-1] + ans[i-1][j] - ans[i-1][j-1] + dp[i][j] - dp[i/2][j/2];
}
}

int main()
{
Init();
int n, m;
while(scanf("%d%d", &n, &m) == 2 && n)
{
if(n < m) std::swap(n, m);
printf("%d\n", ans[n-1][m-1]*2);
}

return 0;
}