二分查找

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二分查找可以说是在经典不过的查找算法了，比如JAVA的库函数里，就有相应的代码实例。如下写出两个版本的二分查找，非递归和递归的

非递归的

public int binarySearch1(int[] a, int key) {
		int low = 0;
		int high = a.length-1;
		int mid;
		while (low <= high) {
			mid = (high + low) >>> 1;
			if (key < a[mid]) {
				high = mid - 1;
			} else if (key > a[mid]) {
				low = mid + 1;
			} else {
				return mid;
			}
		}
		return -1;
	}

递归版的

public int binarySearch2(int[] a, int low, int high, int key) {
		if (low <= high) {
			int mid = (high + low) >>> 1;
			if (key == a[mid]) {
				return mid;
			} else if (key < a[mid]) {
				return binarySearch2(a, low, mid-1, key);
			} else {
				return binarySearch2(a, mid+1, high, key);
			}
		}
		return -1;
	}

二分查找

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原文地址：http://blog.csdn.net/my_jobs/article/details/43566661