Fibosum from SPOJ

Author: kungfucat

FIBOSUM-h.cpp

@@ -0,0 +1,75 @@
+#include<iostream>
+using namespace std;
+
+#define mod 1000000007
+int size=2;
+void multiply(long long int first[][3],long long int second[][3])
+{
+    long long int answer[10][10]={};
+    for(int i=0;i<size;i++){
+        for(int j=0;j<size;j++){
+            for(int k=0;k<size;k++){
+                answer[i][j]=answer[i][j] + (first[i][k]%mod * second[k][j]%mod)%mod;
+                answer[i][j]%=mod;
+            }
+        }
+    }
+    for(int i=0;i<size;i++){
+        for(int j=0;j<size;j++){
+            first[i][j]=answer[i][j];
+        }
+    }
+}
+
+void power(long long int second[][3],long long int n){
+    long long int current[3][3]={},i,j;
+    for(i=0;i<size;i++){
+        for(j=0;j<size;j++)
+            current[i][j]=second[i][j];
+    }
+    if(n<=1){
+        return;
+    }
+    if(n&1){
+         power(second,n-1);
+        multiply(second ,current);
+    }
+    else{
+        power(second,n/2);
+    multiply(second,second);
+    }
+}
+int main(){
+    int t;
+    cin>>t;
+    while(t--){
+        long long int a,b;
+        cin>>a>>b;
+        long long int myArray[3][3]={},answera=0,answerb=0;
+        if(a==0)
+            answera=0;
+        else if(a==1)
+            answera=0;
+        else if(a==2)
+            answera=1;
+        else if(a==3)
+            answera=2;
+        else{
+            myArray[0][0]=1;myArray[0][1]=1;myArray[1][0]=1;myArray[1][1]=0;
+            power(myArray,a);
+            answera=(myArray[0][0]-1)%mod;
+        }
+        
+        if(b<=2){
+            answerb=b;
+        }
+        else{
+            myArray[0][0]=1;myArray[0][1]=1;myArray[1][0]=1;myArray[1][1]=0;
+            power(myArray,b+1);
+            answerb=(myArray[0][0]-1)%mod;
+            
+        }
+        
+        cout<<(answerb-answera+mod)%mod<<"\n";
+    }
+}