Can he touch the borders?
For the following input:
0 0 10 10
10 9 20 20
is there solution? (can he walk like 10,9 ->10,10->11,10, touching
the borders but not walking over them) ?

#include <stdio.h>
#include <math.h>

#define min(a, b) (a < b ? a : b)
#define max(a, b) (a > b ? a : b)
int N;
int read_and_solve()
{
    int i, L = 0;
    int lx1, ly1, lx2, ly2, x1, y1, x2, y2, lo, hi;
    int X = 1, Y = 1;
    scanf("%d %d %d %d %d", &N, &lx1, &ly1, &lx2, &ly2);
    for (i = 1; i < N; i++)
    {
        scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
        lo = max(y1, ly1);
        hi = min(y2, ly2);
        if (hi-lo < 2) return -1;
        if (Y <= lo)  L += (lo+1)-Y, Y = lo+1;
        if (Y >= hi) L += Y-(hi-1), Y = hi-1;
        L += x1-X, X = x1;
        lx1 = x1, ly1 = y1, lx2 = x2, ly2 = y2;
    }
    L += x2-1-X+abs(y2-1-Y);
    return L;
}

void main()
{
    printf("%d\n", read_and_solve());
}

1
0 0 2 2

for
1
0 0 2 2

should the answer be 0

i think that code also answer 0