CODEWITHSUNDEEP
arraysc
江上轻烟
江上轻烟

Reputation: 25

elements in C array strange change

my codes are here. when I print arr[4], sometimes the value is 0, but sometimes the value is 2, it's very strange

#include <stdio.h>
#include <string.h>

int countBalls(int, int);

void main() {
    int res;
    res = countBalls(1, 10);
    printf("result：%d\n", res);
}

int countBalls(int lowLimit, int highLimit)
{
    int i;
    int num=0,max =0,maxNum=0;
    int arr[highLimit];
    memset(arr, 0, highLimit);
    printf("arr[4]:%d\n", arr[4]);
    for(i=lowLimit; i<=highLimit; i++) {
        printf("arr[4]:%d\n", arr[4]);
        return 1;
    }
}

Upvotes: 0

Views: 72

Answers (1)

dbush
dbush

Reputation: 225757

You're not zeroing out the entire array.

memset(arr, 0, highLimit);

The third parameter to memset is the number of bytes to set, not the number of array elements. Assuming an int is 4 bytes, this means you only zero out the first two elements and half of the third.

You need to multiply by the element size.

memset(arr, 0, highLimit * sizeof *arr);

Upvotes: 3

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