Values in array getting altered yet they shouldn't-CodePudding

It's a program that requires the user to enter the values of two 3 by 3 matrix then finds the sum of both matrices and prints out the same together with the added matrices but for some reason after entering the values of both matrices the a value in matrix gets altered then it affects the sum but at times it doesn't

#include<stdio.h>
void main(){
    int matrix1[2][2];
    int matrix2[2][2];
    int sumMatrix[2][2];
    for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
            printf("Matrix[%d][%d]\n", i, j);
            printf("Enter matrix one's values> ");
            scanf("%d", &matrix1[i][j]);
        }
    printf("\n");
    }
     for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
            printf("Matrix[%d][%d]\n", i, j);
            printf("Enter matrix two's values> ");
            scanf("%d", &matrix2[i][j]);
        }
    printf("\n");
     }
    for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
        sumMatrix[i][j] = matrix1[i][j]   matrix2[i][j];
            
        }
    }
    for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
            printf("%d ", matrix1[i][j]);
        }
        printf("\n");}
        printf("\n");
    for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
            printf("%d ", matrix2[i][j]);
        }
        printf("\n");}
        printf("\n");

    for(int i = 0; i<3; i  ){
        for(int j = 0; j<3; j  ){
            printf("%d ", sumMatrix[i][j]);
        }
        printf("\n");

}

}

CodePudding user response：

You're declaring matrixes of size 2x2 and access them as if they were 3x3. What's happening more precisely is a buffer overflow, you write somewhere you shouldn't, and by doing so you overwrite other variables.

CodePudding user response：

Ok so clearly I'm the idiot. I thought array sizes are set based on the number of indices they'll have, so instead of int matrix1[2][2] it should be int matrix [3][3]

CodePudding user response：

Lad, that is array overflow. int matrix1[2][2]; But in the loop, you may get matrix1[2][1], matrix1[2][2].