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Ingy döt Net 2015-02-20 09:02:09 -05:00
parent 00a190b0a6
commit 91df62d461
5697 changed files with 93386 additions and 804 deletions
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28
Task/Quickselect-algorithm/PARI-GP/quickselect-algorithm.pari Normal file
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part(list, left, right, pivotIndex)={
my(pivotValue=list[pivotIndex],storeIndex=left,t);
t=list[pivotIndex];
list[pivotIndex]=list[right];
list[right]=t;
for(i=left,right-1,
if(list[i] <= pivotValue,
t=list[storeIndex];
list[storeIndex]=list[i];
list[i]=t;
storeIndex++
)
);
t=list[right];
list[right]=list[storeIndex];
list[storeIndex]=t;
storeIndex
};
quickselect(list, left, right, n)={
if(left==right,return(list[left]));
my(pivotIndex=part(list, left, right, random(right-left)+left));
if(pivotIndex==n,return(list[n]));
if(n < pivotIndex,
quickselect(list, left, pivotIndex - 1, n)
,
quickselect(list, pivotIndex + 1, right, n)
)
};