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algorithms.c
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/
algorithms.c
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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void incrementByPosition(int a[], int n) {
for (int i = 0; i < n; i++)
a[i] += (i+1);
}
void incrementByPointer(int *a, int n) {
for (int *i = a; i<a+n; i++) {
*i += (i - a + 1);
}
}
void swap(void *a, void *b, size_t s) {
char *temp = malloc(s);
memcpy(temp, a, s);
memcpy(a, b, s);
memcpy(b, temp, s);
free(temp);
}
void selectionSort(int a[], int n) {
for (int s = 0; s < n; s++) {
int min = a[s], mindex = s;
for (int i = s+1; i < n; i++) {
if (a[i] < min) {
min = a[i];
mindex = i;
}
}
swap(a+s, a+mindex, sizeof(int));
}
}
void insertionSort(int a[], int n) {
for (int s = 1; s < n; s++) {
for (int i = s; i > 0; i--) {
if (a[i] < a[i-1])
swap(a+i, a+i-1, sizeof(int));
else break;
}
}
}
int *merge(int a[], int b[], int an, int bn) {
int *c = malloc(sizeof(int)*(an+bn));
int ai = 0, bi = 0, next;
while (ai + bi < an + bn) {
if (ai == an)
next = b[bi++];
if (bi == bn)
next = a[ai++];
if (a[ai] < b[bi])
next = a[ai++];
else next = b[bi++];
c[ai+bi-1] = next;
}
return c;
}
void mergeSort(int a[], int n) {
if (n == 1) return;
int m = n/2;
mergeSort(a, m);
mergeSort(a+m, n-m);
int *tmp = merge(a, a+m, m, n-m);
memcpy(a, tmp, sizeof(int)*n);
free(tmp);
}
void quickSort(int a[], int n) {
if (n < 2) return;
int x = a[0], m = 0;
swap(a, a+n-1, sizeof(int));
for (int i = 0; i < n; i++) {
if (a[i] <= x) {
swap(a+i, a+m, sizeof(int));
m++;
}
}
quickSort(a, m-1);
quickSort(a+m, n-m);
}
int binSearch(int a[], int n, int t) {
int m = n/2;
if (t == a[m]) return m;
if (t < a[m]) return binSearch(a, m, t);
return m+binSearch(a+m, n-m, t);
}
int linSearch(int a[], int n, int t) {
for (int i = 0; i < n; i++) {
if (a[i] == t) return i;
}
}
int gcd(int a, int b) {
if (b) return gcd(b, a%b);
return a;
}
int fib(int n) {
int old = 1, older = 1, cur;
if (n<3) return 1;
for (int i = 0; i < (n-2); i++) {
cur = old + older;
older = old;
old = cur;
}
return cur;
}
int cmp(const int *a, const int *b) {
return *a-*b;
}
int main(void)
{
int list[9] = {5,9,4,3,2,8,7,1,3};
qsort(list, 9, sizeof(int), cmp);
//incrementByPointer(list, 5);
for (int i = 0; i < 9; i++)
printf("%d ", list[i]);
}