replce substr

/*Write a program to Find and Replace a substring from a given string.*/
#include<stdio.h>
#include<string.h>

int main(){
    char stri[20], find[20], repl[20], temp[20], newstri[20], end, mainend, found=1;
    printf("Enter the Main string: ");
    scanf("%s", stri);
    printf("Enter the substring to be found: ");
    scanf("%s", find);
    printf("Enter the substring to be replaced with: ");
    scanf("%s", repl);
    
    for (int i=0; i<=(strlen(stri)-strlen(find)); ++i){
        for(int k=0, j=i; k<strlen(find); ++j, ++k){
            temp[k]=stri[j];
            end=k;
        }
        temp[end+1]='\0';
        if(!strcmp(find, temp)){
            for(int k=0, j=i; k<strlen(repl); ++j, ++k){
                newstri[j]=repl[k];
                end=j+1;
            }
            for(int l=0; stri[i+strlen(find)+l]!='\0'; ++l){
                newstri[end+l]=stri[i+strlen(find)+l];
                mainend=end+l;
            }
            break;
        }
        else {
            for(int k=0; k<=i; ++k){
                newstri[k]=stri[k];
                mainend=k+1;
            }
        }    
    }
    newstri[mainend+1]='\0';
    printf("%s", newstri);
}