c++ - Find the number of ways the N balls could be placed in the M boxes -

you have n different balls numbered 1 n, , m different boxes numbered 1 m.

input:

first line of input contains number of test cases t. after that, next t lines contain value of n , m.

output:

for each test case, print answer. can large, should print modulo 10^9 + 7.

i tried below code, gives error:

#include<iostream> #include<cmath> #include<math.h> using namespace std; int main() {     unsigned short int t;     unsigned long int n,m;     cin>>t;     (int = 0; < t; i++)     {         cin>>n>>m;         long int res;         res=  pow(m,n);             int c=0;             c=pow(10,9);             res=res%(c + 7);         cout<<res<<endl;     }      return 0; } 

you must facing integer overflow problem, that's why must have been getting wrong answer.

do following steps fix problem.

• change unsigned long long long or unsigned long long. (why? think).
• use logarithmic user-defined function calculate value of res = pow(m,n) along modulo consideration side-by-side. boost program.

see code snippet check changes made:

#include<iostream> #define mod 1000000007  int main() {     unsigned short int t;     unsigned long long n , m , result;     unsigned long long power(unsigned long long, unsigned long long); /*prototype of power*/      std::cin>>t;     (int = 0; < t; i++) {         std::cin >> n >> m;         result = power(m , n);         std::cout << result << std::endl;     }      return 0; }  unsigned long long power(unsigned long long m, unsigned long long n) {     if(n == 0) {         return 1;        }      unsigned long long result = power(m , n/2);     result = (result * result) % mod;      if(n%2 == 1) {         result = (result * m) % mod;        }      return result; }