Find Row with Maximum no. of 1’s in Python

April 30, 2022

Row with Maximum no. of 1’s in Python

Here on this page, we will learn how to Find a Row with Maximum no. of 1’s in Python Language.

Example :

  • Input :  matrix  =  [ [ 0, 1, 0, 0 ],
                                     [ 1, 0, 0, 1 ],
                                     [ 1, 1, 1, 1 ],
                                     [ 0, 0, 1, 1 ] ]
  • Output :  3rd Row
Row with Maximum no. of 1’s in Python

Method Discussed :

  • Method 1 : Naïve Method
  • Method 2 : Using Binary Search.

Algorithm ( Method 1 )

  • In this method we will traverse each row of the matrix,
  • Find the count of 1’s in each row.
  • Then compare it with max_count and the index value.
  • After complete iteration, print the value of the index.

Time and Space Complexity :

  • Time-Complexity : O(r*c)
  • Space-Complexity : O(1)
Row with Maximum no. of 1’s

Python Code

Run 
Matrix = [[0, 0, 0, 1],
          [0, 1, 1, 1],
          [1, 1, 1, 1],
          [0, 0, 0, 0]]

max_count, row = 0, -1

for i in range(4):

    count = 0
    for j in range(4):
        if Matrix[i][j] == 1:
            count += 1

    if count > max_count:
        max_count = count
        row = i

print("Row with maximum 1's is :", row+1)

Output

Row with maximum 1's is : 3

Algorithm ( Method 2 )

  • Take a variable to hold the index value of required row, let it be index=-1, and max_count=0, that hold the maximum count of 1.
  • Now, iterate over each row, and take variable say count=0, to count the number of 1’s in current row.
  • For, i-th row, use binary search to find the first instance of 1.
  • Then count = No. of columns – first instance of 1.
  • Check if count > max_count, then set max_count = count and index=i.
  • After the iteration of all rows, print the value of the index.

Time and Space Complexity :

  • Time-Complexity : O(r*log(c))
  • Space-Complexity : O(1)
Run 
def first(arr, low, high):
    
    if high >= low:
        
        mid = low + (high - low) // 2
        if (mid == 0 or arr[mid - 1] == 0) and arr[mid] == 1:
            return mid

        elif arr[mid] == 0:
            return first(arr, (mid + 1), high)

        else:
            return first(arr, low, (mid - 1))

    return -1


Matrix = [[0, 0, 0, 1],
          [0, 1, 1, 1],
          [1, 1, 1, 1],
          [0, 0, 0, 0]]

max_count, row = 0, -1

for i in range(4):

    count = 0
    x = first(Matrix[i], 0, 3)
    if x != -1:
        count = 4 - x
    if count > max_count:
        max_count = count
        row = i

print("Row with maximum 1's is :", row + 1)

Output

Row with maximum 1's is : 3

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2 comments on “Find Row with Maximum no. of 1’s in Python”


  • Harsha

    n=4

    a = [ [ 0, 1, 0, 0 ],
    [ 1, 0, 0, 1 ],
    [ 1, 1, 1, 1 ],
    [ 0, 0, 1, 1 ] ]
    max=0
    for i in range(n):
    num=0

    for j in range(n):
    if a[i][j]==1:
    num=num+1
    if num>max:
    max=num
    index=i
    print(index+1)


  • 5015_Arjun_M

    row, col = [int(x) for x in input().split()]
    mat = []
    for i in range(0, row):
    m = []
    for j in range(0, col):
    m.append(int(input()))
    mat.append(m)
    ones = []
    count1 = 0
    for j in range(1, len(mat[0])+1):
    ones.append(str(j))
    count1 += mat[j-1].count(1)
    ones.append(count1)
    count1 = 0
    rowdict = {ones[i]: ones[i + 1] for i in range(0, len(ones), 2)}
    print(“The rows which have the maximum nos of 1’s are: “)
    maxi = max(rowdict.values())
    for k in rowdict.keys():
    if rowdict[k] == maxi:
    print(k, end = ” “)