sparse matrix addition

#include <stdio.h>
#define MAX 20

void input(int [][MAX],int,int);
void convert_to_triplet(int [][MAX],int,int,int [][3]);
void display(int [][3]);
void addsparse(int [][3],int [][3],int [][3]);

int main()
{
    int r1,c1,r2,c2;

    int matrix1[MAX][MAX];
    int matrix2[MAX][MAX];
    int sparse1[MAX*MAX+1][3];
    int sparse2[MAX*MAX+1][3];
    int result[MAX*MAX+1][3];

    printf("Enter no. of rows and column in first matrix:");
    scanf("%d %d",&r1,&c1);
    do{
                printf("Enter no. of rows and column in second matrix:");
                scanf("%d %d",&r2,&c2);

        }while(r1!=r2||c2!=c1);



    printf("Enter first matrix:\n");
    input(matrix1,r1,c1);

    printf("Enter second matrix:\n");
    input(matrix2,r2,c2);

    convert_to_triplet(matrix1,r1,c1,sparse1);
    convert_to_triplet(matrix2,r2,c2,sparse2);

    printf("Sparse representation of first matrix:\n");
    display(sparse1);

    printf("Sparse representation of second matrix:\n");
    display(sparse2);

    addsparse(sparse1,sparse2,result);

    printf("Resultant matrix is:\n");
    display(result);

    return 0;
}

void input(int a[MAX][MAX],int r,int c){
    int i,j;
    for(i=0;i<r;i++){
        for(j=0;j<c;j++){
            printf("Enter matrix[%d][%d]:",i+1,j+1);
            scanf("%d",&a[i][j]);
        }
    }
}

void convert_to_triplet(int a[][MAX],int r,int c,int  sparse[][3]){
    int i,j,k=1,count=0;

    sparse[0][0]=r;
    sparse[0][1]=c;

    for(i=0;i<r;i++){
        for(j=0;j<c;j++){
            if(a[i][j]){
                sparse[k][0]=i;
                sparse[k][1]=j;
                sparse[k][2]=a[i][j];
                k++;
                count++;
            }
        }
    }

    sparse[0][2]=count;
}

void display(int sparse[][3]){
    int i;
    for(i=0;i<=sparse[0][2];i++){
        printf("%d\t%d\t%d\n",sparse[i][0],sparse[i][1],sparse[i][2]);
    }
}

void addsparse(int a[][3],int b[][3],int c[][3])
{

        int t1,t2,i,j,k;

        if(a[0][0]!=b[0][0]||a[0][1]!=b[0][1]){
              printf("Addition not possible");
    }

        t1=a[0][2];
        t2=b[0][2];
        i=j=k=0;

        c[0][0]=a[0][0];
        c[0][1]=a[0][1];

        while(i<=t1&&j<=t2){
                            if(a[i][0]<b[j][0]){
                                    c[k][0]=a[i][0];
                                    c[k][1]=a[i][1];
                                    c[k][2]=a[i][2];
                                    k++;
                                    i++;

                            }

                            else if(b[j][0]<a[i][0]){
                                    c[k][0]=b[j][0];
                                    c[k][1]=b[j][1];
                                    c[k][2]=b[j][2];
                                    k++;
                                    j++;

                            }

                            else if(a[i][1]<b[j][1]){
                                    c[k][0]=a[i][0];
                                    c[k][1]=a[i][1];
                                    c[k][2]=a[i][2];
                                    k++;
                                    i++;        }

                            else if(b[j][1]<a[i][1]){

                                    c[k][0]=b[j][0];
                                    c[k][1]=b[j][1];
                                    c[k][2]=b[j][2];
                                    k++;
                                    j++;
                            }

                            else {

                                    c[k][0]=a[i][0];
                                    c[k][1]=a[i][1];
                                    c[k][2]=a[i][2]+b[j][2];
                                    k++;
                                    i++;
                                    j++;
                            }
      }

             while(i<=t1){

                        c[k][0]=a[i][0];
                        c[k][1]=a[i][1];
                        c[k][2]=a[i][2];
                        i++;
                        k++;
             }

                while(j<=t2){

                        c[k][0]=b[j][0];
                        c[k][1]=a[j][1];
                        c[k][2]=a[j][2];
                        j++;
                        k++;
                }

                c[0][2]=k-1;
}