Subarrays Divisible by K
JavaScript
Medium
5 views
Problem Description
Count subarrays whose sum is divisible by k.
Input Format
Line1: n k. Line2: n integers.
Output Format
One integer count.
Official Solution
const fs=require('fs');const a=fs.readFileSync(0,'utf8').trim().split(/\\s+/);if(!a[0])process.exit(0);let i=0;const n=Number(a[i++]);const k=Number(a[i++]);let pref=0;const cnt=new Map();cnt.set(0,1);let ans=0n;for(let j=0;j<n;j++){pref=(pref+Number(a[i++]))%k;if(pref<0)pref+=k;ans+=BigInt(cnt.get(pref)||0);cnt.set(pref,(cnt.get(pref)||0)+1);}process.stdout.write(ans.toString());
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