How do i get minimum sum of matrix columns in Java?-CodePudding

So i have this code, which calculates the sum of all columns in matrix and i have to print the smallest sum.

package com.example;

import java.util.Arrays;

public class discrete2 {

    public static void main(String[] args) {

        int a[][] = {
                {0, 1, 1, 0, 1, 0, 0, 1, 0},
                {1, 0, 1, 1, 0, 0, 0, 1, 0},
                {1, 0, 0, 1, 0, 1, 1, 0, 1},
                {0, 1, 0, 0, 0, 1, 0, 0, 1},
                {0, 0, 1, 1, 0, 0, 0, 0, 1},
                {1, 0, 0, 0, 0, 0, 1, 1, 0},
                {0, 0, 0, 0, 1, 1, 1, 0, 0}
        };

        int rows = a.length;
        int cols = a[0].length;

        int sumCol;

        for(int i = 0; i < cols; i  ){
            sumCol = 0;
            for(int j = 0; j < rows; j  ){
                sumCol = sumCol   a[j][i];
            }
            System.out.println("Sum of "   (i 1)  " column: "   sumCol);
        }
    }
}

I tried changing my code to have variable that remembers the smallest number but it's not working somehow and gives out 3, when it should be 2.

CodePudding user response：

public static void main(String[] args) {
    int a[][] = {
            {0, 1, 1, 0, 1, 0, 0, 1, 0},
            {1, 0, 1, 1, 0, 0, 0, 1, 0},
            {1, 0, 0, 1, 0, 1, 1, 0, 1},
            {0, 1, 0, 0, 0, 1, 0, 0, 1},
            {0, 0, 1, 1, 0, 0, 0, 0, 1},
            {1, 0, 0, 0, 0, 0, 1, 1, 0},
            {0, 0, 0, 0, 1, 1, 1, 0, 0}
    };

    int rows = a.length;
    int cols = a[0].length;

    int sumCol;
    int minSumCol = 100000000; // arbitrary large value

    for (int i = 0; i < cols; i  ) {
        sumCol = 0;
        for (int j = 0; j < rows; j  ) {
            sumCol = sumCol   a[j][i];
        }
        minSumCol = Math.min(minSumCol, sumCol);
        System.out.println("Sum of "   (i   1)   " column: "   sumCol);
    }
    System.out.println("Min sum in the matrix is: "   minSumCol);
}

Hi, your code is indeed correct. It does return 2 as the smallest value. This is the output that I got:

Sum of 1 column: 3

Sum of 2 column: 2

Sum of 3 column: 3

Sum of 4 column: 3

Sum of 5 column: 2

Sum of 6 column: 3

Sum of 7 column: 3

Sum of 8 column: 3

Sum of 9 column: 3

Min sum in the matrix is: 2

CodePudding user response：

You have to make little condition outside inner loop for find out the minimum sum of array. Here is down is condition.

if (sumCol < minRow && sumCol > 0){ 
     minRow = sumCol;
     minRowIndex = i   1;
}

Here down is modified code:

package com.example;
import java.util.Arrays;

public class discrete2 {

    public static void main(String[] args) {

        int a[][] = {
                {0, 1, 1, 0, 1, 0, 0, 1, 0},
                {1, 0, 1, 1, 0, 0, 0, 1, 0},
                {1, 0, 0, 1, 0, 1, 1, 0, 1},
                {0, 1, 0, 0, 0, 1, 0, 0, 1},
                {0, 0, 1, 1, 0, 0, 0, 0, 1},
                {1, 0, 0, 0, 0, 0, 1, 1, 0},
                {0, 0, 0, 0, 1, 1, 1, 0, 0}
        };

        int rows = a.length;
        int cols = a[0].length;

        int sumCol;
        int minRow = Integer.MAX_VALUE;
        int minRowIndex = 0;

        for(int i = 0; i < cols; i  ){
            sumCol = 0;
            for(int j = 0; j < rows; j  ){
                sumCol  = a[j][i];
            }
            System.out.println("Sum of Row "   (i   1)  " is: "   sumCol);
            // Find minimum sum of array
            if (sumCol < minRow && sumCol > 0){ 
                minRow = sumCol;
                minRowIndex = i   1;
            }
        }

        // Print minimum sum of array
        System.out.println("-------------------------------");
        System.out.println("Row "   minRowIndex   " has the minimum sum of "   minRow);
    }
}