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三分查找—有序数组

晗韩不普通 2022-04-16 阅读 110
#include<bits/stdc++.h>
using namespace std;

int temp1 = 0;		//用于判断是否已经找到  1-找到
void three_find_x(int a[], int left, int right, int x) {	//三分查找,位序
	int mid_left = left + (right - left) / 3;
	int mid_right = right - (right - left) / 3;

	//先判是否相等,当mid_left==mid_right时,若不等,则此处无法结束,下一个if直接结束,避免多调用一次函数
	if (x == a[mid_left]) {
		temp1 = 1;
		cout << mid_left << endl;
		return;
	}
	if (mid_left >= mid_right) {
		return;
	}
	if (x < a[mid_left]) {
		three_find_x(a, left, mid_left - 1, x);
	}
	if (x > a[mid_left]) {
		if (x == a[mid_right]) {
			temp1 = 1;
			cout << mid_right << endl;
			return;
		}
		if (x > a[mid_right]) {
			three_find_x(a, mid_right + 1, right, x);
		}
		if (x < a[mid_right]) {
			three_find_x(a, mid_left + 1, mid_right - 1, x);
		}
	}
}

int main() {
	int N;
	cin >> N;
	int a[10000] = {};
	int i, j, temp;
	for (i = 1; i <= N; i++) {
		cin >> a[i];
	}

	int x;
	cin >> x;
	three_find_x(a, 1, N, x);
	if (temp1 == 0) {
		cout << -1 << endl;
	}
	return 0;
}

测试结果:

 

 

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