Understand insertion sort and selection sort in seconds

Insertion sort principle: It works by constructing an ordered sequence, for unsorted data, scan from back to front in the sorted sequence, find the corresponding position and insert.

Insertion sorting core: Assuming that the first element is arranged, the elements after the arrangement are compared from the back to the front and moved one by one.

Insertion sort implementation:

 

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print ?

1. void insertion_sort(int a[], int n)  
2. {  
3.     int i,j,tmp;  
4.     for (i = 1; i < n; i++) {  
5.         tmp = a[i];  
6.         for (j = i - 1; j >= 0 && a[j] > tmp; j--) {  
7.             a[j+1] = a[j];  
8.         }  
9.         a[j+1] = tmp;  
10.     }  
11. }  

void insertion_sort(int a[], int n)
{
	int i,j,tmp;
	for (i = 1; i < n; i++) {
		tmp = a[i];
		for (j = i - 1; j >= 0 && a[j] > tmp; j--) {
			a[j+1] = a[j];
		}
		a[j+1] = tmp;
	}
}

Insertion sort process animation:

Selection sort:

 

Similar to selection sort and insertion sort, both are in-place comparison sorts.

 

The core idea of ​​selection sorting: the first part of the unsorted part is taken as the smallest (largest), and then compared with the rest in turn, if there is a smaller (larger), write down the subscript and use this as the new smallest (maximum) value, continue to compare, after one pass, then swap with the first one.

 

Selection sort implementation:

 

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1. void selection_sort(int a[], int n)  
2. {  
3.     int i, j, k;  
4.     for (i = 0; i< n-1; i++) {  
5.         k = i;  
6.         for (j = i+1; j < n; j++) {  
7.             if (a[k] > a[j])  
8.                 k = j;  
9.         }  
10.         if (k != i) {  
11.             int tmp = a[i];  
12.             a[i] = a[k];  
13.             a[k] = tmp;  
14.         }  
15.     }  
16. }  

void selection_sort(int a[], int n)
{
	int i, j, k;
	for (i = 0; i< n-1; i++) {
		k = i;
		for (j = i+1; j < n; j++) {
			if (a[k] > a[j])
				k = j;
		}
		if (k != i) {
			int tmp = a[i];
			a[i] = a[k];
			a[k] = tmp;
		}
	}
}

Selection sort process animation: