1. Start
2. Define a structure poly with fields: expo (exponent) and coeff (coefficient).
3. Ask for the number of terms for polynomial x1, and then get their coefficients and exponents.
4. Do the same for polynomial x2.
5. Create a result array res with a size equal to the larger of the two input polynomial sizes.
6. Set pointers i, j, and k to 0 (for x1, x2, and res respectively).
7. Addition Process:
    Loop until both x1 and x2 have been processed:
    If x1 exponent > x2 exponent: Copy x1 term to res and move to next term in x1.
    If x2 exponent > x1 exponent: Copy x2 term to res and move to next term in x2.
    Else: Add x1 and x2 coefficients, store in res with their common exponent. Move to next terms in both x1 and x2.
    If there are remaining terms in either polynomial, copy them to res.
8. Display the resultant polynomial.
9. End

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#include <stdio.h>

struct poly {
    int expo;
    int coeff;
};

int main()
{
    int n,m;
    printf("Enter the number of terms of x1: ");
    scanf("%d", &n);
    
    struct poly x1[n];
    printf("Enter values for x1\n");
    for (int i = 0; i < n; i++){
        printf("Enter coeffiecient of term %d: ", i + 1);
        scanf("%d", &x1[i].coeff);
        printf("Enter exponent of term %d: ", i + 1);
        scanf("%d", &x1[i].expo);
    }
    
    printf("\n");
    printf("Enter the number of terms of x2: ");
    scanf("%d", &m);
    
    struct poly x2[m];
    printf("Enter values for x2\n");
    for (int i = 0; i < m; i++){
        printf("Enter coeffiecient of term %d: ", i + 1);
        scanf("%d", &x2[i].coeff);
        printf("Enter exponent of term %d: ", i + 1);
        scanf("%d", &x2[i].expo);
    }
    printf("\n");
    
    int resSize = (n > m) ? n : m;
    struct poly res[resSize];
    
    // addition
    int i = 0, j = 0, k = 0;
    while (i < n && j < m)
    {
        if (x1[i].expo > x2[j].expo)
        {
            res[k].expo = x1[i].expo;
            res[k].coeff = x1[i].coeff;
            i++;
        }
        else if (x1[i].expo < x2[j].expo)
        {
            res[k].expo = x2[j].expo;
            res[k].coeff = x2[j].coeff;
            j++;
        }
        else
        {
            res[k].coeff = x1[i].coeff + x2[j].coeff;
            res[k].expo = x1[i].expo;
            i++;
            j++;
        }
        k++;
    }
    
    while (i < n)
    {
        res[k].expo = x1[i].expo;
        res[k].coeff = x1[i].coeff;
        i++;
        k++;
    }
    
    while (j < m)
    {
        res[k].expo = x2[j].expo;
        res[k].coeff = x2[j].coeff;
        j++;
        k++;
    }
    
    printf("Resultant polynomial\n");
    printf("Exponent: ");
    for (i = 0; i < k; i++){
        printf("%d ", res[i].expo);
    }
    printf("\n");
    
    printf("Coefficient: ");
    for (i = 0; i < k; i++){
        printf("%d ", res[i].coeff);
    }
    
    printf("\n");
}