给出一个有效的算法来确定在整数A1

数据结构与算法分析——c语言描述 练习2.11

二分搜索改一下就行，只不过判断的是数列的下标。

</pre><pre name="code" class="cpp">#include<stdio.h>

#define MAXN 1000
int a[MAXN];

bool binarySearch(int low, int high) {
	while (low <=high) {
		int mid = (low + high) / 2;
		if (a[mid] > mid+1)
			high = mid - 1;
		else if (a[mid] < mid+1)
			low = mid + 1;
		else 
			return true;
	}
	return false;
}

int main() {
	int n;
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
		scanf("%d", &a[i]);

	if (binarySearch(0, n - 1))
		printf("yes\n");
	else
		printf("no\n");
}