ACwing算法基础课_1

原文链接:here

快速排序模板

void quick_sort(int q[],int l,int r) {
	if(l>=r) return;
	int x=q[l+r >> 1],i=l-1,j=r+1;
	while(i<j) {
		do i++;
		while(q[i]<x);
		do j--;
		while(q[j]>x);
		if(i<j) swap(q[i],q[j]);
	}
	quick_sort(q,l,i-1);
	quick_sort(q,j+1,r);
}

归并排序模板

void merge_sort( int q[], int l, int r ) {
	if ( l >= r )
		return;
	int mid = l + r >> 1;
	merge_sort( q, l, mid );
	merge_sort( q, mid + 1, r );
	int k = 0, i = l, j = mid + 1;
	while ( i <= mid && j <= r )
		if ( q[i] <= q[j] )
			tmp[k++] = q[i++];
		else tmp[k++] = q[j++];
	while ( i <= mid )
		tmp[k++] = q[i++];
	while ( j <= r )
		tmp[k++] = q[j++];
	for ( i = l, j = 0; i <= r; i++, j++ )
		q[i] = tmp[j];
}

整数二分算法模板

// 检查x是否满足某种性质
bool check(int x) {
/* ... */
}
// 区间[l, r]被划分成[l, mid]和[mid + 1, r]时使用：
int bsearch_1(int l, int r) {
	while (l < r) {
		int mid = l + r >> 1;
		if (check(mid)) r = mid; else l = mid + 1;
	}
	return l;
}
// 区间[l, r]被划分成[l, mid - 1]和[mid, r]时使用：
int bsearch_2(int l, int r) {
	while (l < r) {
		int mid = l + r + 1 >> 1;
		if (check(mid)) l = mid; else r = mid - 1;
	}
	return l;
}

浮点数二分算法模板

// 检查x是否满足某种性质
bool check(double x) {
	/* ... */
}
double bsearch_3(double l, double r) {
const double eps = 1e-6;
// eps 表示精度，取决于题目对精度的要求
while (r - l > eps) {
	double mid = (l + r) / 2;
	if (check(mid)) r = mid; else l = mid;
}
return l;
}