lostCity

# 智力题：3个5和1个1的四则运算如何使其结果为24
# 下面是tcl简单解决办法。没有玩过的不妨想想，然后再看程序实现。
#
set vlist "5.00 5.00 5.00 1.00"
set func "+ - * /"
set result 24
set possNo 0
set findout 0
# a b c d = 24 = 5*(5-1/5)
for {set i 0} {$i<4} {incr i} {
    for {set j 0} {$j<4} {incr j} {
        if {$i==$j} {continue}
        for {set k 0} {$k<4} {incr k} {
            if {$i==$k||$j==$k} {continue}
            for {set l 0} {$l<4} {incr l} {
                if {$i==$l||$j==$l||$k==$l} {continue}
                set a [lindex $vlist $i]
                set b [lindex $vlist $j]
                set c [lindex $vlist $k]
                set d [lindex $vlist $l]
                foreach f1 $func {
                    foreach f2 $func {
                        foreach f3 $func {
                            set expl ""
                            # 0
                            lappend  expl "$a $f1 $b $f2 $c $f3 $d"
                            # 1
                            lappend  expl "($a $f1 $b) $f2 $c $f3 $d"
                            lappend  expl "($a $f1 $b $f2 $c) $f3 $d"
                            lappend  expl "$a $f1 ($b $f2 $c) $f3 $d"
                            lappend  expl "$a $f1 ($b $f2 $c $f3 $d)"
                            lappend  expl "$a $f1 $b $f2 ($c $f3 $d)"
                            # 2
                            lappend  expl "($a $f1 $b) $f2 ($c $f3 $d)"
                            foreach exp $expl {
                                if {$findout} {break}
                                set exp [join $exp ""]
                                incr possNo
                                if {[catch {
                                    if {[expr abs($exp-$result)]<=0.0001} {
                                        puts "$possNo: $exp = [expr 1.00*$exp]"
                                        set findout 1
                                        break
                                     } 
                                } ierr]} {
                                }
                            }
                            if {$findout} {break}
                        }
                        if {$findout} {break}
                    }
                    if {$findout} {break}
                }
                if {$findout} {break}
            }  
            if {$findout} {break}
        }  
        if {$findout} {break}
    }  
    if {$findout} {break}
}