http://acdream.info/problem?pid=1007
题目大意,给你n个数,输出这n个数的k次方的和,注意最后的结果得是正数。
刚开始因为模乘法没有考虑好,一直死wa不过,后来在模乘法中特判一下,终于ac了。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<cstdio> typedef long long LL; const LL MOD = 10000000007LL; int n; LL k, temp, sum; LL mul_mod(LL a, LL b) { LL res = 0; int flag = (b < 0); b = (b ^ (b >> 63)) - (b >> 63); while(b) { if(b & 1) res = (res + a) % MOD; b >>= 1; a = (a << 1) % MOD; } res %= MOD; return (flag ? (~res + 1) : res); } LL calc(LL a, LL k) { LL res = 1; while(k) { if(k & 1) res = mul_mod(a, res) % MOD; k >>= 1; a = mul_mod(a, a) % MOD; } return res; } int main() { int tCase; scanf("%d", &tCase); while(tCase--) { sum = 0; scanf("%lld%lld", &n, &k); for(int i = 0; i < n; ++ i) { scanf("%lld", &temp); sum = (sum + calc(temp, k)) % MOD; } printf("%lld ", (sum + MOD) % MOD); } return 0; }