Largest subarray with 0 sum

#1

question–>
https://practice.geeksforgeeks.org/problems/largest-subarray-with-0-sum/1#
code–>

int maxLen(int a[], int n)
{
    unordered_map<int,int> m;
    int pre=0;
    int maxi=INT_MIN;
    for(int i=0;i<n;i++){
        pre+=a[i];
        if(pre==0 ){
            if(m.count(pre)){
                maxi=max(maxi,i+1);
            }
            else{
                m[pre]=i;
            }
        }
        else{
            if(m.count(pre)){
                maxi=max(maxi,i-m[pre]);
            }
            else{
                m[pre]=i;
            }
        }
    }
    
    return maxi==INT_MIN?0:maxi;
}

not passing all testcases

#2

Hey @sheikhhaji18
Because if pre is 0 then max subarray will be from start always i.e a0 +a1+…+ai==0

        if(pre==0 ){
            // if(m.count(pre)){
                maxi=max(maxi,i+1);
            // }
            // else{
            //     m[pre]=i;
            // }
        }
#3

ohh there is no need to insert 0 to hashmap ,okay got it passing all testcases,;

1 Like
#4

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