//Im trying to ask for the user input and I am unable to get it to work. I know there is a way to do this without functions, but I want to have my main function separate from the algorithm. I want the output to display the correct level inputted.

#include <stdio.h>
int main () {
    int levels, i, j, result;
    printf("Please enter how many levels of Pascal's Triangle you would like to see:");
    scanf("%d",&levels);
    newfunc();
}
int newfunc() {
    int levels, i, j, result;
    int num[28];
    for(i=0; i < levels; i  ) {
        num[i] = 1;
        for (j = i - 1; j > 0; j--) {
            num[j]  = num[j - 1];
            }
            result = (levels - i);
            for (j = 0; j <= i; j  ) {
                printf("%d ", num[j]);
            
            
            }
            printf("\n");
    }
} 

CodePudding user response：

Not sure about infinite. In newfunc():

1. levels is not initialized so it could be very large number.
2. If level >= 28 then num will overflow and anything could happen as you overwrite memory (most likely a segmentation fault).
3. result is not used.
4. The function doesn't return anything.
5. Not a bug but as negative values don't make sense for your problem switch from int to unsigned. Note comment for 2nd loop.

#include <stdio.h>

void newfunc(unsigned levels) {
    // protect against vla overflow
    if(levels > 1000) return;
    unsigned num[levels];
    for(unsigned i = 0; i < levels; i  ) {
        num[i] = 1;
        // when i = 0 it causes j to underflow so add i > 0
        for (unsigned j = i - 1; i > 0 && j > 0; j--) {
            num[j]  = num[j - 1];
        }
        for (unsigned j = 0; j <= i; j  ) {
            printf("%u ", num[j]);
        }
        printf("\n");
    }
}

int main () {
    unsigned levels;
    printf("Please enter how many levels of Pascal's Triangle you would like to see:");
    scanf("%u", &levels);
    newfunc(levels);
}

Example session:

Please enter how many levels of Pascal's Triangle you would like to see:7
1 
1 1 
1 2 1 
1 3 3 1 
1 4 6 4 1 
1 5 10 10 5 1 
1 6 15 20 15 6 1 

When you look at the output you may notice that it's left/right symmetric, so you could change the algorithm to only calculate i/2 1 of num and then tweak the print loop only use the "left" part of num when needing to the right side of the triangle.

CodePudding user response：

You should declare 'int newfunc()' before 'int main()'. So try like this.

#include <stdio.h>
int newfunc();
int main () {
    int levels, i, j, result;
    printf("Please enter how many levels of Pascal's Triangle you would like to see:");
    scanf("%d",&levels);
    newfunc();
}
int newfunc() {
    int levels, i, j, result;
    int num[28];
    for(i=0; i < levels; i  ) {
    num[i] = 1;
    for (j = i - 1; j > 0; j--) {
        num[j]  = num[j - 1];
        }
        result = (levels - i);
        for (j = 0; j <= i; j  ) {
            printf("%d ", num[j]);
        
        
        }
        printf("\n");
    }
}