线段树--求区间最大差值

最新推荐文章于 2023-07-15 21:38:03 发布

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本文介绍如何使用线段树数据结构求解区间内的最大差值问题。通过构造线段树并进行最大值和最小值的更新与查询，可以高效地处理区间查询。代码中展示了线段树的构建、查询过程以及主函数的应用。

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#include <stdio.h>
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) > (b) ? (b) : (a))

#define MAXN 50000

int num[MAXN] = {0};

struct SegmentTree
{
	int left;
	int right;
	int maxValue;
	int minValue;
}dwSegmen[4 * MAXN];

int maxValue = 0;
int minValue = 0;

void constrcutMax(int index, int left, int right)
{
	dwSegmen[index].left = left;
	dwSegmen[index].right = right;
	if (left == right)
	{
		dwSegmen[index].maxValue = dwSegmen[index].minValue = num[left];
		return;
	}
	int mid = (left + right) >> 1;
	constrcutMax((index << 1) + 1, left, mid);
	constrcutMax((index << 1) + 2, mid + 1, right);
	dwSegmen[index].maxValue = MAX(dwSegmen[(index << 1) + 1].maxValue, dwSegmen[(index << 1) + 2].maxValue);
	dwSegmen[index].minValue = MIN(dwSegmen[(index << 1) + 1].minValue, dwSegmen[(index << 1) + 2].minValue);
}

void QueryMax(int index, int left, int right)
{
	if (dwSegmen[index].left == left && dwSegmen[index].right == right)
	{
		maxValue = maxValue > dwSegmen[index].maxValue ? maxValue : dwSegmen[index].maxValue;
		minValue = minValue < dwSegmen[index].minValue ? minValue : dwSegmen[index].minValue;
		return;
	}
	int mid = (dwSegmen[index].left + dwSegmen[index].right) >> 1;
	if (right <= mid)
	{
		QueryMax((index << 1) + 1, left, right);
	}
	else if (left > mid)
	{
		QueryMax((index << 1) + 2, left, right);
	}
	else
	{
		QueryMax((index << 1) + 1, left, mid);
		QueryMax((index << 1) +2, mid + 1, right);
	}
}

int main()
{
	int n = 0;
	int q = 0;
	scanf("%d %d",&n, &q);
	for (int i = 0; i < n; ++i)
	{
		scanf("%d",&num[i]);
	}
	constrcutMax(0, 0, n - 1);
	while (q--)
	{
		int a = 0;
		int b = 0;
		scanf("%d %d",&a, &b);
		if (a > b)
		{
			a = a ^ b;
			b = a ^ b;
			a = a ^ b;
		}
		maxValue = 0;
		minValue = 1000001;
		QueryMax(0, a - 1, b - 1);
		printf("%d\n",maxValue - minValue);
	}
	return 0;
}