Programs/subarray.cpp at master · Pritam099/Programs · GitHub

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//print subarrays of an array
#include<iostream>
using namespace std;

int main(){
    int n;
    cin >> n;
    int a[n];

    for(int i = 0; i < n; i++){
        cin>>a[i];
    }

    for(int i = 0; i < n; i++){
        for(int j = i; j < n; j++){
            for(int k = i; k <= j; k++){
                cout << a[k] << " ";
            }

            cout << endl;
        }
    }

}

//Maximum subarray sum brute force approach, time complexity O(n^3)
#include<iostream>
#include<climits>
#include<algorithm>
using namespace std;

int main(){
    int n;
    cin >> n;
    int a[n];

    for(int i = 0; i < n; i++){
        cin>>a[i];
    }

    int max_sum = INT_MIN;
    for(int i = 0; i < n; i++){
        for(int j = i; j < n; j++){
            int sum = 0;
            for(int k = i; k <= j; k++){
                sum+=a[k];
            }
            max_sum = max(max_sum,sum);
        }
    }
    cout << max_sum;
}

//Maximum subarray sum, time complexity O(n^2) [cumulative sum approach]
#include<iostream>
#include<climits>
#include<algorithm>
using namespace std;

int main(){
    int n;
    cin>>n;
    int a[n];

    for(int i=0 ; i<n ; i++){
        cin>>a[i];
    }

    int curr_sum[n+1];
    curr_sum[0] = 0;

    for(int i = 1; i<=n; i++){
        curr_sum[i] = curr_sum[i-1] + a[i-1];
    }

    int max_sum = INT_MIN;
    for(int i=1; i<=n; i++){
        int sum=0;
        for(int j=0; j<i; j++){
            sum = curr_sum[i] - curr_sum[j];
            max_sum = max(max_sum,sum);
        }
    }
    cout << max_sum;

}

//Maximum subarray sum, time complexity O(n)[Kadane's algorithm]
#include<iostream>
#include<climits>
#include<algorithm>
using namespace std;

int main(){
    int n;
    cin>>n;
    int a[n];

    for(int i=0; i<n; i++){
        cin>>a[i];
    }
    int max_sum = INT_MIN;
    int currsum=0;
    for(int i=0; i<n; i++){
        currsum+=a[i];
        //update sum as 0 if sum becomes negative
        if(currsum<0){
            currsum = 0;
        }
        max_sum = max(max_sum,currsum);
    }

    cout << max_sum;
}