Merging multiple sorted arrays in C

Question

Trying to merge 8 pre-sorted arrays. I'm fairly new to C, but this is what I've come up with so far. Needless to say it doesn't work. What I can't figure out is why. I've based it off the C++ mergesort implementation here and tried to extend it to 8 dimensions and simplify it a bit, but for some reason it tends to give me the elements of the first array, followed by 34, 30 then it repeats 23 until the end. It doesn't even pick up that 21 is the smallest value on the first iteration. ``` int test1[5] = {23, 24, 25, 33, 51}; int test2[5] = {21, 34, 44, 50, 62}; int test3[5] = {34, 36, 41, 44, 46}; int test4[5] = {30, 31, 32, 35, 40}; int test5[5] = {54, 56, 57, 58, 60}; int test6[5] = {31, 33, 36, 51, 52}; int test7[5] = {44, 46, 76, 78, 79}; int test8[5] = {23, 33, 43, 54, 63}; int output[40]; int t1, t2, t3, t4, t5, t6, t7, t8; t1 = 0; t2 = 0; t3 = 0; t4 = 0; t5 = 0; t6 = 0; t7 = 0; t8 = 0; int p = 0; int temp1; int temp2; while(p < 40) { if (t1 < 5) { temp1 = 1; temp2 = test1[t1]; }e…

Accepted Answer

This is why you get the first 5 elements of the first array:

```
if (t1 < 5) {
        temp1 = 1;
        temp2 = test1[t1];
```

Your code is specifically ensuring the first 5 elements of the first array get selected first. You should be comparing the value of the next element in test1 against the next element in the other arrays, not just blindly picking it. Also, your use of if..then..else if.. else if... is not correct. If you find out that array 2's next element is less than array 1's next element, you still have to examine whether arrays 3, 4 and 5 are less.

Try structuring your code like this

```
int temp1 = -1;
if (t1 < 5) {
    temp1=1;
    temp2=test1[t1];
}
if ((t2 < 5) && ((temp1 < 0) || (test2[t2] < temp2))) {
    temp1=2;
    temp2=test2[t2];
}
if (t3...
```

followed by your existing switch statement.

Merging multiple sorted arrays in C

Solution

Problem