1. PermCheck 桃花顺检验 Check whether array A is a permutation.

package com.code;

import java.util.Arrays;

public class Test04_2 {
    public static int solution(int[] A) {
        int size = A.length;
        if(size == 1){
            return A[0]==1?1:0;
        }
        Arrays.sort(A);
        for(int i=0;i<size;i++){
            if(A[i]!=i+1){
                return 0;
            }
        }
        return 1;
    }
    public static void main(String[] args) {
        int [] a = {1,1,3,4};
        System.out.println(solution(a));
    }
}

/**
1. PermCheck 桃花顺检验
Check whether array A is a permutation.
A non-empty zero-indexed array A consisting of N integers is given.

A permutation is a sequence containing each element from 1 to N once, and only once.

For example, array A such that:

    A[0] = 4
    A[1] = 1
    A[2] = 3
    A[3] = 2
is a permutation, but array A such that:

    A[0] = 4
    A[1] = 1
    A[2] = 3
is not a permutation, because value 2 is missing.

The goal is to check whether array A is a permutation.

Write a function:

class Solution { public int solution(int[] A); }

that, given a zero-indexed array A, returns 1 if array A is a permutation and 0 if it is not.

For example, given array A such that:

    A[0] = 4
    A[1] = 1
    A[2] = 3
    A[3] = 2
the function should return 1.

Given array A such that:

    A[0] = 4
    A[1] = 1
    A[2] = 3
the function should return 0.

Assume that:

N is an integer within the range [1..100,000];
each element of array A is an integer within the range [1..1,000,000,000].
Complexity:

expected worst-case time complexity is O(N);
expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).
Elements of input arrays can be modified.
*/