搜索算法

搜索往往是建立在排好序的基础上的
二分查找

public class BinarySearch {
    public int search(int[] nums, int target) {
        int n = nums.length;
        int i = 0, j = n, m;
        while (i < j) {
            m = i + (j - i) / 2;
            if (nums[m] == target) {
                return m;
            } else if (nums[m] < target) {
                i = m + 1;
            } else {
                j = m;
            }
        }
        return -1;
    }
}

public class TestBinarySearch {
    public static void main(String[] args) {
        int[] a = {0,1,2,3,4,5,6,7,8,9};
        int target = (int)(15*Math.random());
        System.out.println(target);
        System.out.println(binarySearch(a,target));
    }

    public static int binarySearch(int[] a,int target){
        int i = 0,j = a.length-1,mid;
        while (i<=j){
            mid = i + (j-i)/2;
            if (a[mid] == target){
                return mid;
            } else if (a[mid] < target){
                i = mid + 1;
            } else {
                j = mid - 1;
            }
        }
        return -1;
    }
}