shell 编程实例练习（二）

1.冒泡排序：

#for((i=0;i<10;i++))
for i in {0..9}  #两种方法都可以
do
    ((a[i]=$RANDOM % 1000)) #产生随机数
    echo -n "${a[i]} "
done
function bubble()
{
    len=${#a[@]}
    for((i=0;i<len;i++))
    do
        for((j=i;j<len;j++))
        do
            if [ ${a[i]} -ge ${a[j]} ]
            then
                tmp=${a[i]}
                ((a[i]=a[j]))
                ((a[j]=tmp))
            fi
        done
    done
}

bubble
echo 
echo "After bubble: "
for((i=0;i<10;i++))
do
    echo -n "${a[i]} "
done

运行结果：

2.求数组的最大子序列和：

#a=(-2 11 -4 13 -5 -2)
function maxSum() #数组a是在后面定义 但是maxSum里面已经可用，可见a是全局的
{
    #local a="$*"
    #local len="$#"
    ((currSum=0))
    ((mSum=0))
    len=${#a[@]}
        for((i=1;i<len;i++))
        do
            ((currSum=currSum+a[i]))
            #echo "a[i]: ${a[i]}"
            #echo "F: $currSum"
            if [ $currSum -gt $mSum ]
                then
                    #echo "S: $currSum"
                    ((mSum=currSum))
            elif [ $currSum -lt "0" ]
                then
                ((currSum=0))
            fi
        done
    return $mSum
}

a=(-2 11 -4 13 -5 -2)
#maxSum "${a[@]}"
maxSum
echo $?

运行结果：

3. 二分查找：

binarySearch()
  {
      v=$1
      #an="$1[@]"
      #a=${!an}
      a=${array[@]}
      #echo "len an ${#an[*]}"
      #echo "a  ${#array[*]}"
      #echo an 
      for i in $a
      do
         ar[i]=$i
         #echo $i
     done
     #echo "len $ar "
     low=1
     high=${#ar[*]}
     (( times=0 ))
 
     while (( low <= high ))
     do
         (( ++times ))
         (( mid=(low+high)/2 ))
         #echo -n " mid="$mid
         #echo -n " ar[mid]="${ar[mid]}
         if (( v > ar[mid] ))
         then
             (( low = mid + 1 ))
         elif (( v < ar[mid] ))
         then
             (( high = mid - 1 ))
         else
             #echo -e "/nTimes="$times
             return $mid
         fi
     done
 
     #echo -e "/nTimes="$times
     echo "can not find" 
     return -1
 }
 
 for ((i=1;i<=100;++i))
 do
     (( array[i] = i ))
 done
 

binarySearch 2
echo -e "$?\ttimes"
binarySearch 8
echo -e "$?\ttimes"
binarySearch 101
echo -e "$?\ttimes"
 exit 0

运行结果：

不知道为什么不可以 return -1 ？？？