在 C++ 中查找数组中可能移动后左指针的索引
在这个问题中,我们给定一个大小为 N 的数组 arr[]。我们的任务是查找数组中可能移动后左指针的索引。
我们有两个数组指针,一个左指针和另一个右指针。
左指针从索引 0 开始,其值递增。
右指针从索引 (n-1) 开始,其值递减。
如果遍历的总和小于另一个,则指针的值增加,即如果左指针的总和小于右指针的总和,则左指针增加,否则右指针减少。并且总和更新。
让我们举个例子来理解这个问题,
Input : arr[] = {5, 6, 3, 7, 9, 4} Output : 2
说明 -
leftPointer = 0 -> sum = 5, rightPointer = 5 -> sum = 4. Move rightPointer leftPointer = 0 -> sum = 5, rightPointer = 4 -> sum = 13. Move leftPointer leftPointer = 1 -> sum = 11, rightPointer = 4 -> sum = 13. Move leftPointer leftPointer = 2 -> sum = 14, rightPointer = 4 -> sum = 13. Move rightPointer leftPointer = 2 -> sum = 14, rightPointer = 3 -> sum = 20. Move rightPointer Position of the left pointer is 2.
解决方案方法
解决此问题的一个简单方法是根据总和移动 leftPointer 和 rightPointer。然后检查 leftPointer 是否比 rightPointer 大 1。
示例
程序说明我们解决方案的工作原理
#include <iostream> using namespace std; int findIndexLeftPointer(int arr[], int n) { if(n == 1) return 0; int leftPointer = 0,rightPointer = n-1,leftPointerSum = arr[0], rightPointerSum = arr[n-1]; while (rightPointer > leftPointer + 1) { if (leftPointerSum < rightPointerSum) { leftPointer++; leftPointerSum += arr[leftPointer]; } else if (leftPointerSum > rightPointerSum) { rightPointer--; rightPointerSum += arr[rightPointer]; } else { break; } } return leftPointer; } int main() { int arr[] = { 5, 6, 3, 7, 9, 4 }; int n = sizeof(arr) / sizeof(arr[0]); cout<<"The index of left pointer after moving is "<<findIndexLeftPointer(arr, n); return 0; }
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输出
The index of left pointer after moving is 2
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