PHP merge sorting (merge sorting)-algorithm principle analysis

: This article mainly introduces PHP merge sorting (merge sorting)-algorithm principle analysis. if you are interested in PHP tutorials, please refer to it. Merge sorting: The time complexity is ~ O (nlogn) -- also known as merge sorting

The Merge sorting method combines two (or more) ordered tables into a new ordered table,

That is, the sequence to be sorted is divided into several ordered subsequences, and then the ordered subsequences are merged into the overall ordered sequence.

 StableSort ($ arrStoreList, function ($ a, $ B) {// function ($ a, $ B) anonymous function return $ a <$ B ;}); // the static call method is also optional./* Merge_sort: stableSort ($ arrStoreList, function ($ a, $ B) {return $ a <$ B ;}); */print_r ($ arrStoreList); class Merge_sort {public static function stableSort (& $ array, $ cmp_function = 'strcmp ') {// use the merge sort self :: mergeSort ($ array, $ cmp_function); return;} public static function mergeSort (& $ array, $ cmp_function = 'strcmp ') {// Arrays of size <2RequireNo action. if (count ($ array) <2) {return;} // Split the array in half $ halfway = count ($ array)/2; $ array1 = array_slice ($ array, 0, $ halfway); $ array2 = array_slice ($ array, $ halfway); // Recurse to sort the two halves self: mergeSort ($ array1, $ cmp_function); self:: mergeSort ($ array2, $ cmp_function); // If all of $ array1 is <= all of $ array2, just append them. // array1 and array2 are in different order. arra needs to be compared The size of the last element of y1 and the first element of array2 if (call_user_func ($ cmp_function, end ($ array1), $ array2 [0]) <1) {$ array = array_merge ($ array1, $ array2); return;} // combine two ordered arrays into an ordered array: merge the two sorted arrays into a single sorted array $ array = array (); $ ptr1 = $ ptr2 = 0; while ($ ptr1 <count ($ array1) & $ ptr2 <count ($ array2) {if (call_user_func ($ cmp_function, $ array1 [$ ptr1], $ array2 [$ ptr2]) <1) {$ array [] = $ ar Ray1 [$ ptr1 ++];} else {$ array [] = $ array2 [$ ptr2 ++];} // Merge the remainder while ($ ptr1 <count ($ array1) {$ array [] = $ array1 [$ ptr1 ++];} while ($ ptr2 <count ($ array2) {$ array [] = $ array2 [$ ptr2 ++];} return ;}}?>

Output result: Array ([0] => 5 [1] => 4 [2] => 3 [3] => 2 [4] => 1)

Algorithm principle analysis: The key is to understand the principle of recursive calls and return functions.

The above introduces PHP merge sorting (merge sorting)-algorithm principle analysis, including The require content, hope to be helpful to friends who are interested in PHP tutorials.