Arranging arbitrary rectangles to fill a space

Haskell, 226 bytes

((y,z):l)&(w,x)|x*y<1=(w+y,x+z):l
(q:l)&p=p:q:l
(p@(u,v):r@(y,z):l)%q@(w,x)=[((y-w,z):l)&q&(u,v-x)|w<=y,x<=v]++[p:m|m<-(r:l)%q]
_%_=[]
g m(p:n)l=any(g[]$m++n)(l%p)||g(p:m)n l
g[]_[_,_,_]=0<1
g _[]_=0<0
($[(0,9^9),(9^9,0)]).g[]

Try it on Ideone

How it works

This recursively searches for all partial tilings whose shape is a Young diagram, adding one rectangle at a time, and checks whether any of the final results are rectangles.

To see that any tiling of a rectangle can be built this way: in any tiling of a nonempty Young diagram, let R be the set of rectangles in the tiling whose southwest corner does not touch any other rectangle. Since each concave vertex of the Young diagram is edge-adjacent (not merely corner-adjacent) to at most one rectangle in R, and the number of these concave vertices is one less than the number of rectangles in R, there must be at least one rectangle in R that is edge-adjacent to none of these concave vertices. Removing it yields another Young diagram, so we can proceed by induction.


C, 1135 1158 1231 1598 bytes

Well, it's past the stated deadline, but seeing as how there are no answers yet, here's one (a bit long) in C.

Returns:

  • 0 (zero) on failure (don't fit)
  • Full fitting matrix on success

Update:

Original code could get stuck on some matrices, taking much longer than the allowed 10s. Current revision should complete all matrices in under 1s. This is accomplished by 1) Sorting the input rectangles and 2) skipping repeated sizes when fitting.

Golfed:

#define R r[i]
#define Z return
#define _(B,D,E) for(int B=E;B<D;B++)
struct{int x,y,u,p;}r[25],*S;int A,M,N,U,V,X,Y;char *P;T(x,y,w,h){_(I,x+w,x)_(J,y+h,y)if(I/U|J/V|P[J*U+I])Z 0;Z 1;}L(x,y,w,h,c){_(I,x+w,x)_(J,y+h,y)P[J*U+I]=c;}F(){int x=0,y;while(++x<A)if(!P[x])break;if(x/A){_(i,V,0)printf("%*.*s\n",U,U,P+i*U);exit(0);}y=x/U;x-=y*U;_(i,N,0)if(!R.u&T(x,y,R.x,R.y))R.u=1,L(x,y,R.x,R.y,'A'+i),F(),R.u=0,L(x,y,R.x,R.y,0);}O(i,y){if(!R.u){if(!T(0,y,R.x,R.y))Z;R.u=1;R.p=0;L(0,y,R.x,R.y,'A'+i);y+=R.y;}if(y-V||F())_(j,N,0)if(j-i&!r[j].u){O(j,y);while(r[j].x-r[j+1].x|r[j].y-r[j+1].y)j++;}R.u=0;L(R.p,(y-=R.y),R.x,R.y,0);}Q(i,x){if(!R.u){if(R.x>U-x)Z;R.u=1;R.p=x;L(x,0,R.x,R.y,'A'+i);x+=R.x;}if(x-U||O(i,1))_(j,N,0)if(j-i&!r[j].u)Q(j,x);L(x-=R.x,0,R.x,R.y,0);R.u=0;}C(int*a,int*b){Z*a-*b?*a-*b:a[1]-b[1];}main(){_(i,25,0)if(++N&scanf("%d%d\n",&R.x,&R.y)-2)break;_(i,N,0){A+=R.x*R.y;if(R.x>X)X=R.x;if(R.y>Y)Y=R.y;}_(i,A+1,1)if(!(A%i)){if(i<Y|A/i<X)continue;M++;S=realloc(S,M*16);S[M-1].y=i;S[M-1].x=A/i;}qsort(S,M,16,C);P=calloc(A+1,1);_(j,M,0){U=S[j].x;V=S[j].y;_(i,N,0)R.u=1,L(0,0,R.x,R.y,'A'+i),Q(i,R.x),R.u=0;}printf("0\n");exit(1);}

UnGolfed:

#define R r[i]
#define Z return
#define _(B,D,E) for(int B=E;B<D;B++)
struct {
    int x,y,u,p;
} r[25],*S;
int A,M,N,U,V,X,Y;
char *P;

test_space(x,y,w,h) {
    _(I,x+w,x)
        _(J,y+h,y)
            if (    I >= U |
                    J >= V |
                    P[J*U+I]) Z 0;
    Z 1;
}
place_rect(x,y,w,h,c){
    _(I,x+w,x)
        _(J,y+h,y)P[J*U+I] = c;
}

fill_rest() {
    int x=0,y;
    while(++x<A) if (!P[x])break;
    if (x>=A) {
        _(i,V,0) printf("%*.*s\n", U,U, P+i*U);
        exit(0);
    }
    y = x / U; x -= y*U;

    _(i,N,0)
        if (!R.u & test_space(x, y, R.x, R.y))
                R.u = 1,
                place_rect(x, y, R.x, R.y, 'A'+i),
                fill_rest(),
                R.u = 0,
                place_rect(x, y, R.x, R.y, 0);

}

fill_y(i,y) {
    if (!R.u) {
        if (!test_space(0, y, R.x, R.y)) Z;
        R.u = 1;
        R.p = 0;
        place_rect(0, y, R.x, R.y, 'A'+i);
        y += R.y;
    }
    if (y == V) fill_rest();
    else _(j,N,0)
        if (j!=i && !r[j].u){ fill_y(j, y);
        while (r[j].x^r[j+1].x||r[j].y^r[j+1].y)j++;
        }
    R.u = 0;
    place_rect(R.p, (y -= R.y), R.x, R.y, 0);
}

fill_x(i,x) {
    if (!R.u) {
        if (R.x > U - x) Z;
        R.u = 1;
        R.p = x;
        place_rect(x, 0, R.x, R.y, 'A'+i);
        x += R.x;
    }
    if (x == U) fill_y(i, 1);
    else
        _(j,N,0)
            if (j!=i && !r[j].u) fill_x(j, x);
    place_rect((x -= R.x), 0, R.x, R.y, 0);
    R.u = 0;
}
C(int*a,int*b) {
    Z *a^*b?*a-*b:a[1]-b[1];
}


main() {
    _(i,25,0)
        if (++N&&scanf("%d %d\n", &R.x, &R.y)!=2) break;
    _(i,N,0){
        A+=R.x*R.y;
        if(R.x>X)X=R.x;
        if(R.y>Y)Y=R.y;
    }
    _(i,A+1,1)
        if (!(A%i)) {
            if (i < Y | A/i < X) continue;
            M++;
            S = realloc(S,M*16);
            S[M-1].y=i;
            S[M-1].x=A/i;
        }
    qsort(S, M, 16,C);
    P = calloc(A + 1,1);
    _(j,M,0){
        U = S[j].x; V = S[j].y;
        _(i,N,0)
            R.u = 1,
            place_rect(0, 0, R.x, R.y, 'A'+i),
            fill_x(i, R.x),
            R.u = 0;
    }
    printf("0\n");
    exit(1);
}

Explanation: We have 6 functions: main, O, Q, F, L and T. T tests to see if there is space for the rectangle at a given spot. L fills a rectangle into the output buffer or, alternately removes one by overwriting it. O and Q build up the left and top walls, respectively and F fills the remainder of the rectangle by iterative search.

Although the basic search is iterative, we eliminate the vast majority of possible search vectors, first by building up the allowed combinations of width and height for the master rectangle and then eliminating impossible configurations. Additional speed could be gained in larger rectangles by determining bottom and right walls prior to filling the center but it is not required for decent speed when limiting to 25 interior rectangles.

Tags:

Code Golf

Tiling

Set Partitions

Decision Problem

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