demo地址：https://github.com/weiman152/PaiXu.git
选择排序是先比较，并不急着交换，而是记录最小的值的位置，把最小的值与第一个位置的值进行交换。然后第二轮的时候，再次遍历除了第一个位置的之外的其他数字，找出最小的，放在第二个位置。以此类推，最后得出排序后的数组。假如数组的个数为n，选择排序会进行 n+(n-1)+(n-2)+......+2+1次比较，最多进行n次交换。下面进行举例说明：（这里为了更加容易理解，把每一次的比较都列了出来）
1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48
i: 第几轮比较
min: 当前最小值的下标
j: 同一轮中每一个值与最小值的比较
i=0://第一轮 min = 0 （步骤中用 m 代表）
j=1: 1(m), 16(), 23, 56, 89, 33, 7, 27, 55, 37, 48
j=2: 1(m), 16, 23(), 56, 89, 33, 7, 27, 55, 37, 48
j=3: 1(m), 16, 23, 56(), 89, 33, 7, 27, 55, 37, 48
j=4: 1(m), 16, 23, 56, 89(), 33, 7, 27, 55, 37, 48
j=5: 1(m), 16, 23, 56, 89, 33(), 7, 27, 55, 37, 48
j=6: 1(m), 16, 23, 56, 89, 33, 7(), 27, 55, 37, 48
j=7: 1(m), 16, 23, 56, 89, 33, 7, 27(), 55, 37, 48
j=8: 1(m), 16, 23, 56, 89, 33, 7, 27, 55(), 37, 48
j=9: 1(m), 16, 23, 56, 89, 33, 7, 27, 55, 37(), 48
j=10: 1(m), 16, 23, 56, 89, 33, 7, 27, 55, 37, 48()
第一轮比较完成结果：(找到最小值1，放到第一个位置,共比较了 n-1 次)
结果： 1(m), 16, 23, 56, 89, 33, 7, 27, 55, 37, 48
i=1://第二轮 min = 1
j=2: 1(️), 16(m), 23(), 56, 89, 33, 7, 27, 55, 37, 48
j=3: 1(️), 16(m), 23, 56(), 89, 33, 7, 27, 55, 37, 48
j=4: 1(️), 16(m), 23, 56, 89(), 33, 7, 27, 55, 37, 48
j=5: 1(️), 16(m), 23, 56, 89, 33(), 7, 27, 55, 37, 48
j=6: 1(️), 16(m), 23, 56, 89, 33, 7(), 27, 55, 37, 48
j=7: 1(️), 16, 23, 56, 89, 33, 7(m), 27(), 55, 37, 48
j=8: 1(️), 16, 23, 56, 89, 33, 7(m), 27, 55(), 37, 48
j=9: 1(️), 16, 23, 56, 89, 33, 7(m), 27, 55, 37(), 48
j=10: 1(️), 16, 23, 56, 89, 33, 7(m), 27, 55, 37, 48()
比较完成之后交换 ：
1(️), 7(m), 23, 56, 89, 33, 16, 27, 55, 37, 48
第二轮比较结果：
1(️), 7(m), 23, 56, 89, 33, 16, 27, 55, 37, 48
i=2://第三轮 min = 2
j=3:1(️), 7(️), 23(m), 56(), 89, 33, 16, 27, 55, 37, 48
j=4:1(️), 7(️), 23(m), 56, 89(), 33, 16, 27, 55, 37, 48
j=5:1(️), 7(️), 23(m), 56, 89, 33(), 16, 27, 55, 37, 48
j=6:1(️), 7(️), 23(m), 56, 89, 33, 16(), 27, 55, 37, 48
j=7:1(️), 7(️), 23, 56, 89, 33, 16(m), 27(), 55, 37, 48
j=8:1(️), 7(️), 23, 56, 89, 33, 16(m), 27, 55(), 37, 48
j=8:1(️), 7(️), 23, 56, 89, 33, 16(m), 27, 55, 37(), 48
j=8:1(️), 7(️), 23, 56, 89, 33, 16(m), 27, 55, 37, 48()
交换:1(️), 7(️), 16(m), 56, 89, 33, 23, 27, 55, 37, 48()
第三轮比较结果：
1(️), 7(️), 16(m), 56, 89, 33, 23, 27, 55, 37, 48
i=3://第四轮 min = 3
j=4:1(️), 7(️), 16(️), 56(m), 89(), 33, 23, 27, 55, 37, 48
j=5:1(️), 7(️), 16(️), 56(m), 89, 33(), 23, 27, 55, 37, 48
j=6:1(️), 7(️), 16(️), 56, 89, 33, 23(), 27, 55, 37, 48
j=7:1(️), 7(️), 16(️), 56, 89, 33, 23(m), 27(), 55, 37, 48
j=8:1(️), 7(️), 16(️), 56, 89, 33, 23(m), 27, 55(), 37, 48
j=9:1(️), 7(️), 16(️), 56, 89, 33, 23(m), 27, 55, 37(), 48
j=10:1(️), 7(️), 16(️), 56, 89, 33, 23(m), 27, 55, 37, 48()
交换：1(️), 7(️), 16(️), 23(m), 89, 33, 56, 27, 55, 37, 48
第四轮比较结果：
1(️), 7(️), 16(️), 23(m), 89, 33, 56, 27, 55, 37, 48
.........
四轮比较下来，确认了前四个最小值。
下面我们就使用不同语言把代码写出来吧。
OC语言：
main函数：
#import <Foundation/Foundation.h>
#import "Sort.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
//选择排序
NSMutableArray * arr2= [NSMutableArray arrayWithArray:@[@1,@16,@23,@56,@89,@33,@7,@27,@55,@37,@48]];
NSArray * select = [sort selectedSortWithArray:arr2];
NSLog(@"选择： %@",select);
}
return 0;
}
Sort类：
Sort.h：
#import <Foundation/Foundation.h>
@interface Sort : NSObject
/**
选择排序
@param array 排序前的数组
@return 排序后的数组
*/
- (NSArray *)selectedSortWithArray:(NSMutableArray *)array;
Sort.m:
#import "Sort.h"
@implementation Sort
- (NSArray *)selectedSortWithArray:(NSMutableArray *)array {
NSMutableArray * arr = [array mutableCopy];
int min = 0;
for (int j = 0; j<arr.count-1; j++) {
min = j;//最小值下标记录
for (int i = j+1; i<arr.count; i++) {
if (arr[min] > arr[i]) {
min = i;
}
}
if (min!=j) {
[arr exchangeObjectAtIndex:min withObjectAtIndex:j];
}
}
return arr;
}
@end
Swift语言
main.swift
import Foundation
let mySort: Sort = Sort()
let arr2: [Int] = [1,16,23,56,89,33,7,27,55,37,48]
mySort.selectedSort(array: arr2)
Sort.swift
//
// Sort.swift
// Sort_Swift
//
// Created by iOS on 2018/3/13.
// Copyright © 2018年 weiman. All rights reserved.
//
import Cocoa
class Sort: NSObject {
/// 选择排序
///
/// - Parameter array: 需要排序的数组
func selectedSort(array: [Int]) {
var arr = array
//记录最小值的下标
var min = 0;
for i in 0..<arr.count-1 {
min = i
for j in i+1..<arr.count {
if arr[j] < arr[min] {
min = j
}
}
if min != i {
arr.swapAt(i, min)
}
}
print("选择排序： \(arr)")
}
}
C语言
//
// main.c
// Sort_C
//
// Created by iOS on 2018/3/13.
// Copyright © 2018年 weiman. All rights reserved.
//
#include <stdio.h>
void selectedSort(int a[], int size);
int main(int argc, const char * argv[]) {
printf("Hello, World!\n");
int arr[] = {1,16,23,56,89,33,7,27,55,37,48};
int sizeA = sizeof(arr)/sizeof(arr[0]);
selectedSort(arr, sizeA);
for(int i=0; i<sizeA; i++){
printf(" %d ",arr[i]);
}
printf("\n");
return 0;
}
/**
选择排序
@param a 排序的数组
@param size 数组的长度
*/
void selectedSort(int a[], int size){
int min = 0;
for (int i = 0; i< size-1; i++) {
min = i;
for (int j=i+1; j<size; j++) {
if (a[j]<a[min]) {
min = j;
}
}
if (min != i) {
int tmp = a[i];
a[i] = a[min];
a[min] = tmp;
}
}
}
排序前： [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
打印下排序执行的每一个步骤：
i:0,j:1 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:2 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:3 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:4 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:5 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:6 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:7 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:8 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:9 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:0,j:10 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:2 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:3 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:4 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:5 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:6 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:7 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:8 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:9 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:1,j:10 [1, 16, 23, 56, 89, 33, 7, 27, 55, 37, 48]
i:2,j:3 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:4 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:5 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:6 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:7 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:8 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:9 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:2,j:10 [1, 7, 23, 56, 89, 33, 16, 27, 55, 37, 48]
i:3,j:4 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:5 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:6 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:7 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:8 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:9 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:3,j:10 [1, 7, 16, 56, 89, 33, 23, 27, 55, 37, 48]
i:4,j:5 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:4,j:6 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:4,j:7 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:4,j:8 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:4,j:9 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:4,j:10 [1, 7, 16, 23, 89, 33, 56, 27, 55, 37, 48]
i:5,j:6 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:5,j:7 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:5,j:8 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:5,j:9 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:5,j:10 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:6,j:7 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:6,j:8 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:6,j:9 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:6,j:10 [1, 7, 16, 23, 27, 33, 56, 89, 55, 37, 48]
i:7,j:8 [1, 7, 16, 23, 27, 33, 37, 89, 55, 56, 48]
i:7,j:9 [1, 7, 16, 23, 27, 33, 37, 89, 55, 56, 48]
i:7,j:10 [1, 7, 16, 23, 27, 33, 37, 89, 55, 56, 48]
i:8,j:9 [1, 7, 16, 23, 27, 33, 37, 48, 55, 56, 89]
i:8,j:10 [1, 7, 16, 23, 27, 33, 37, 48, 55, 56, 89]
i:9,j:10 [1, 7, 16, 23, 27, 33, 37, 48, 55, 56, 89]
选择排序结果：
[1, 7, 16, 23, 27, 33, 37, 48, 55, 56, 89]
