smallest 3 elements in 2- dimensional matrix

Question

Here i have some problems with find smallest 3 elements in 2- dimensional matrix in C

here is my code:

for (i=0; i<r; i++) {
    for (j=0; j<c; j++) {
        if (m[i][j] < min1) {
            min1 = m[i][j];
            indexi_1 = i;
            indexj_1 = j;
        }
        if (m[i][j] < min2 && indexi_1 != i && indexj_1 != j) {
            min2 = m[i][j];
            indexi_2 = i;
            indexj_2 = j;
        }
    }
    for (j=0; j<c; j++) {
        if (m[i][j] < min3 && m[i][j] != m[indexi_1][indexj_1] && m[i][j] != m[indexi_2][indexj_2]) {
            min3 = m[i][j];
            indexi_3 = i;
            indexj_3 = j;
        }
    }
}

with matrix like this

int m[r][c] = {{33,  4, 23,  2}, {5,  3, 24, 16}, {8, 31,  7,  4},{10,  5,  2,  6}};

getting this output:

 Local minimum (value=2) - row=0, column=3.
 Local minimum (value=2) - row=3, column=2.
 Local minimum (value=4) - row=0, column=1.

so as you see here, the problem only with last min element, i think it doused because of index.

Answer 1

You compare the third minimum against the values of temporary min1 and min2. You must move the third loop after the outer for loop

for (i=0; i<r; i++) {
    for (j=0; j<c; j++) {
        if (m[i][j] < min1) {
            min1 = m[i][j];
            indexi_1 = i;
            indexj_1 = j;
        }
        if (m[i][j] < min2 && indexi_1 != i && indexj_1 != j) {
            min2 = m[i][j];
            indexi_2 = i;
            indexj_2 = j;
        }
    }
}

for (i=0; i<r; i++) {
    for (j=0; j<c; j++) {
        if (m[i][j] < min3 && m[i][j] != m[indexi_1][indexj_1] && m[i][j] != m[indexi_2][indexj_2]) {
            min3 = m[i][j];
            indexi_3 = i;
            indexj_3 = j;
        }
    }
}

Now the last loop will compare against the final first two minima.

Answer 2

Here:

if (m[i][j] < min3 &&
    m[i][j] != m[indexi_1][indexj_1] &&
    m[i][j] != m[indexi_2][indexj_2])

You compare values instead of indices.

Answer 3

Change this line

if (m[i][j] < min3 && m[i][j] != m[indexi_1][indexj_1] && m[i][j] != m[indexi_2][indexj_2])

to

if (m[i][j] < min3 && (indexi_1 != i && indexj_1 != j) && (indexi_2 != i && indexj_2 != j))