Question

This could be considered a homework question.
This problem is wel known: “you have a triangle of numbers and you have to find the greatest sum“

well no problem, I’ve made a solution in python some time ago, works flawless.
But now in c++, the solution is 75256, my answer is 9729.
So the problem is that the type short overflows.

So to fix this, I assumed changing my array to type int would solve everything.. but then, when declaring an array a[1001][1001] it freezes (i guess memory error).

anyone know what to do?
I tried something with another int, and whenever the value in a got bigger than 32767 it would increment, but my solution then still is off 300? (the code works – tested on many smaller ones)

#include <iostream>
#include <fstream>

int main() {
    std::ofstream fout ("numtri.out");
    std::ifstream fin  ("numtri.in");
    short trifield[1001][1001] = {0};
    int Rows, tmp=0;
    fin >> Rows;
    for (int x = 0; x<Rows;x++) 
        for (int nr = 0; nr<=x;nr++){
            fin >> tmp;
            trifield[x][nr] = tmp;}

    for (int y = (Rows-2); y > -1; y--)
        for (int x = 0; x <= y+1; x++) {
            int a = trifield[y+1][x];
            int b = trifield[y+1][x+1];
            if (a > b) trifield[y][x] += a;
            else       trifield[y][x] += b;
        }
    fout << trifield[0][0] << std::endl;
    return 0;    
}

note: I’m not looking for the solution, just a good way to deal with overflows, examples appreciated!

Answer 1

You get a stack overflow instead of a numeric overflow!

Move the array to static memory outside of main, so it doesn’t use the stack.