1049-deg-route

http://www.ifrog.cc/acm/problem/1049

I usually look for the law in these maths problems.

First the violence simulates the previous ones, and then finds (x, y) = (x, y-1) + (x-1, y) gets.

But it's useless. Because to get (x, y-1) These, but also recursive processing, will be GG.

Then find the rule is C (x + y, y)-C (x + y, y-1)

Cannot nothing more yy. Try to match the relationship between X and Y.

Generally must be related to these two numbers, and 2 * x these few relationships.

#include <cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<algorithm>#defineIOS Ios::sync_with_stdio (False)using namespacestd;#defineINF (0X3F3F3F3F)typedefLong Long intLL; #include<iostream>#include<sstream>#include<vector>#include<Set>#include<map>#include<queue>#include<string>ConstLL MOD = 1e4 +7; ll Quick_pow (ll a,ll b,ll MOD) {//solving the value of a a^b%modLLBase=a%MOD; LL ans=1;//multiplied, so here is 1     while(b) {if(b&1) {ans= (ans*Base)%mod;//If this is a big data, use Quick_mul.        }        Base=(Base*Base)%mod;//Notice//note here that each time the base is its own base timesb>>=1; }    returnans;} ll C (ll n,ll m,ll MOD) {if(n<m)return 0;//To prevent SB from circulating in the time of Lucas    if(n==m)return 1; LL ans1=1; LL Ans2=1; LL MX=max (N-M,M);//this is also necessary. It's about the biggest one.LL mi=n-MX;  for(inti =1; I <= mi; ++i) {ans1= ans1* (mx+i)%MOD; Ans2= ans2*i%MOD; }    return(Ans1*quick_pow (ans2,mod-2, MOD)%mod);//Put it in the last place, or it'll be slow.}ll Lucas (ll n,ll m,ll MOD) {ll ans=1;  while(N && m &&ans) {ans=ans*c (n%mod,m%mod,mod)%MOD; N/=MOD; M/=MOD; }    returnans;} LL Calc (ll X, ll y) {ll ans= (Lucas (2* x, X, MOD) + Mod-lucas (2* x, X +1, MOD))%MOD; returnans;}voidWork () {LL x, y; CIN>> x >>y; if(Y = =0) {cout<<1<<Endl; } Else {        if(x = =y) {cout<< Calc (x, y) <<Endl; } Else{cout<< (Lucas (x + y, y, MOD)-Lucas (x + y, y-1, MoD) + MoD)% mod <<Endl; }    }}intMain () {#ifdef local freopen ("Data.txt","R", stdin);#endif//For (x = 1; x <=; ++x) {//For (y = 0; y <= x; ++y) {//Work ();//        }//cout << Endl;//    }IOS; intT; CIN>>T;  while(t--) work (); return 0;}

1049-deg-route