Read the How to prepare for an interview series at my blog: http://se7so.blogspot.com/2014/01/how-to-prepare-for-interview.html

prob6.cpp

void resetMtrx(vector<vector<int> >& mtrx) {

    if(mtrx.size() == 0 || mtrx[0].size() == 0) return;

    int rows[mtrx.size()], cols[mtrx[0].size()];

    memset(rows, 1, sizeof rows);
    memset(cols, 1, sizeof cols);

    for(int i = 0; i < mtrx.size(); i++) {
        for(int j = 0; j < mtrx[i].size(); j++) {
            if(mtrx[i][j] == 0) {
                rows[i] = cols[j] = 0;
            }
        }
    }
    
    for(int i = 0; i < mtrx.size(); i++)
	for(int j = 0; j < mtrx[i].size(); j++)
	if(rows[i] || cols[j]) mtrx[i][j] = '0'; 
}