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Hash_PrintAllZeroSumSubArrays.java
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Hash_PrintAllZeroSumSubArrays.java
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
// https://practice.geeksforgeeks.org/problems/zero-sum-subarrays/0/
// https://practice.geeksforgeeks.org/problems/subarray-with-0-sum/0 , Hash_SubArrayWithZeroSum (Similar problem)
// https://ide.geeksforgeeks.org/MgGndmGeRW (a good solution)
// https://www.geeksforgeeks.org/print-all-subarrays-with-0-sum/
public class Hash_PrintAllZeroSumSubArrays {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int t = Integer.parseInt(br.readLine().trim());
while (t-- > 0) {
int n = Integer.parseInt(br.readLine().trim());
String[] str = br.readLine().trim().split("\\s+");
long[] ip = new long[n];
for (int i = 0; i < n; i++) {
ip[i] = Long.parseLong(str[i]);
}
System.out.println(getAllZeroSumSubArrays(ip));
//System.out.println(zeroSumSubArrays.size());
}
}
private static long getAllZeroSumSubArrays(long[] ip) {
Map<Long, Integer> prefixSumFreqMap = new HashMap<>(); // map stores prefixSum and it's frequency
int count = 0;
long prefixSum = 0;
prefixSumFreqMap.put(0L, 1); // handling special case for zero.
for (long value : ip) {
prefixSum += value;
count += prefixSumFreqMap.getOrDefault(prefixSum, 0); // get all the frequency of this prefixSum
prefixSumFreqMap.put(prefixSum, prefixSumFreqMap.getOrDefault(prefixSum, 0) + 1); // add this prefixSum to map
}
System.out.println(prefixSumFreqMap);
return count;
}
}