等值首尾和

最新推荐文章于 2024-05-24 17:45:51 发布

原创最新推荐文章于 2024-05-24 17:45:51 发布 · 1.9k 阅读

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本文介绍了一种算法，用于在一个数组中找到具有相同前置和后置和的元素对。通过遍历数组并计算每个元素的前置和与后置和，算法能够高效地找出满足条件的元素对。此过程涉及对数组元素进行加法操作，并通过比较前置和与后置和来确定是否匹配。

假设有一个数组x[]，它有n个元素，每一个都大于0，称x[0] + x[1] + ... + x[i]是个前置和，而x[j] + x[j + 1] + ... + x[n - 1]则是后置和，请写一个程序，求出x[]中有多少组相同的前置和和后置和

题目虽然很简单，可是还是。。。

#include <iostream>
#include <iterator>
#include <algorithm>
#include <vector>

using namespace std;

int array[] = {1, 2, 2, 1};
const int size = sizeof array / sizeof *array;

int findGominator(int *array, int size)
{
	if (array == NULL || size <= 0)
		return -1;

	int leftIndex = -1;
	int rightIndex = size;
	int prefix = 0;
	int suffix = 0;
	int count = 0;

	while (leftIndex < size && rightIndex >= 0)
	{
		if (prefix < suffix)
		{
			leftIndex++;
			prefix += array[leftIndex];
		}
		else if (prefix > suffix)
		{
			rightIndex--;
			suffix += array[rightIndex];
		}
		else if (prefix == suffix && prefix != 0)
		{
			count++;
			cout << "leftIndex = " << leftIndex << endl;
			cout << "rightIndex = " << rightIndex << endl;
			leftIndex++;
			rightIndex--;
			prefix += array[leftIndex];
			suffix += array[rightIndex];
		}
		else
		{
			leftIndex++;
			rightIndex--;
			prefix += array[leftIndex];
			suffix += array[rightIndex];
		}
	}

	return count;
}

void main()
{
	int ret = findGominator(array, size);

	cout << "ret = " << ret << endl;
}

#include <iostream>
#include <cmath>

using namespace std;

void main()
{
	int array[] = {1, 2, 3, 4, 4, 3, 2, 1};
	const int size = sizeof array / sizeof *array;

	int leftIndex = 0;
	int rightIndex = size - 1;
	int prefixSum = array[0];
	int suffixSum = array[size - 1];

	while (leftIndex < size && rightIndex >= 0)
	{
		if (prefixSum == suffixSum)
		{
			cout << "prefixSum = " << prefixSum << endl;
			cout << "suffixSum = " << suffixSum << endl;
			leftIndex++;
			rightIndex--;
			prefixSum += array[leftIndex];
			suffixSum += array[rightIndex];
		}
		else if (prefixSum < suffixSum)
		{
			leftIndex++;
			prefixSum += array[leftIndex];
		}
		else if (prefixSum > suffixSum)
		{
			rightIndex--;
			suffixSum += array[rightIndex];
		}
	}
}