在C中找到零的第一行nxn数组

Question

I have some pseudocode that finds the first all-zero row in an nxm matrix:

int first_zero_row = -1; /* none */
int i, j;
for(i=0; i<n; i++) {
    for (j=0; j<n; j++) {
       if (A[i][j]) goto next;
    }
    first_zero_row = i;
    break;
next: ;
}

While this should work, I don't think using a goto statement is the best way to go. I'm not very familiar with C but my goal is to have the code as well structured in C as possible. Would this be the best way to go about it, or is there a faster or more general way?

Answer 1

Just set first_zero_row only when the inner loop ran to completion,

int first_zero_row = -1; /* none */
int i, j;
for(i=0; i<n; i++) {
    for (j=0; j<n; j++) {
       if (A[i][j]) break;
    }
    if (j == n) {
        first_zero_row = i;
        break;
    }
}

if you want to avoid the goto .

Answer 2

Place break; statement instead of goto statement. Set a boolean flag and check for the flag and if the flag is true, then break again from outer for loop too. Something like this -

bool nonZeroFlag = true;

for(i=0; i<n; i++) {
   for (j=0; j<n; j++) {
     if (A[i][j]){
        nonZeroFlag = false;
        break;
     }
   }
  if (nonZeroFlag) {
     first_zero_row = i;
     break;
  }
  nonZeroFlag = true;
}

Answer 3

int first_zero_row = -1; /* none */
int i, j;
for(i=0; i<n; i++) {
    for (j=0; j<n; j++) {
       if (A[i][j] != 0){
           first_zero_row = i;
       } 
    }
    break;
next: ;
}

how about this?

Answer 4

Here is one with no break or goto :)

int zero_count = -1; /* none */
i = j = 0;
for(i=0; i < n && (zero_count != n); i++) {
    for (j=0; j < n && (A[i][j] == 0); j++) {
       zero_count = j + 1;
    }
}

if(i < 10)
   printf("First Zero row is %d\n",i);
else
   printf("Nop! Not today!\n");