# Is anybody can point out what is wrong with my solution?

• ``````public void setZeroes(int[][] matrix) {
long zero_rows = 0, zero_columns = 0;
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[0].length; j++) {
if (matrix[i][j] == 0) {
zero_rows |= (1 << i);
zero_columns |= (1 << j);
}
}
}

for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[0].length; j++) {
if (((zero_rows >> i) & 1) > 0 || ((zero_columns >> j) & 1) > 0) {
matrix[i][j] = 0;
}
}
}
}
``````

I didn't pass the case 152.

151 / 154 test cases passed.

But there are only 50 rows and 51 columns in this case.

Is there anybody can help me with this problem?

Thanks!

• First of all, nice solution! Although I think you are aware of that it only works for matrix with certain size limitation.

Then, although you use "long" specifier for zero_rows and zero_columns, there are two things to watch out here.

1. long is not guaranteed to have 64 bit length, it is only true for 64-bit system. Therefore using long long instead of long is safer and more compatible.

2. this statement is actually harming you even if you are working on 64-bit system:

"zero_rows |= (1 << i);"

To be specific, immediate numbers will be interpreted as int by default, and shifting an int by more than 32 is undefined behavior. Therefore 1 << 50 may well end not to be 2^49 as you thought.

That being said, if you still want to use this solution to pass the test, try use (1LL << i) instead, while you put letters "LL" after 1 to indicate it's a "long long".

• Hi dragonmigo,

Thank you for answering my question.

You are right! The problem is that I used (1 << i) instead of (1L << i). So when the number of rows or columns is larger than 32, it'll not correct any more.

I changed my code as following:

zero_rows |= (1L << i);
zero_columns |= (1L << j);

Then it passed the case #152. Although this solution won't pass the larger case # 156, which has 154 columns.

I'm not sure about how long type actually works in JVM. I'll look it up in java document.

Thanks!

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