stringPermHeap.asm

;;permutation of strings using heap's algorithm

org 100h

.data
intro db "Permutation of string using Heap's Algorithm$"
string db "abcde$"
strLen = ($ - string) - 1
c dw strLen dup(0)
newLine db 0ah, 0dh, "$"
i dw 0

.code
mov dx, offset intro
mov ah, 09h
int 21h
mov dx, offset newLine
int 21h
mov dx, offset newLine
int 21h
mov dx, offset string
int 21h
mov dx, offset newLine
int 21h

while:
mov bx, i
cmp bx, strLen
jnl endWhl
    push bx
    add bx, bx
    mov cx, c[bx]
    pop bx
    cmp cx, i
    jnl else
        mov ax, i
        mov dx, 0
        mov si, 2
        div si

        cmp dx, 0
        jne notEven
            push ax
            mov ah, string[0]
            xchg ah, string[bx]
            xchg ah, string[0]
            pop ax
            jmp endNotZero
        notEven:
            push ax
            push bx
            add bx, bx
            mov di, c[bx]
            pop bx
            mov ah, string[di]
            xchg ah, string[bx]
            xchg ah, string[di]
            pop ax
        endNotZero:
            mov dx, offset string
            mov ah, 09h
            int 21h
            mov dx, offset newLine
            int 21h
            push bx
            add bx, bx
            inc c[bx]
            pop bx
            mov i, 0
        jmp while
    else:
        push bx
        add bx, bx
        mov c[bx],0
        pop bx
        inc i
        jmp while
endWhl:

hlt