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  • CodeChef Little Elephant and Balance

    Given an array A1,A2...AN, you have to print the size of the largest contiguous subarray such that
    LCM of all integers in that subarray is equal to the product of all integers in that subarray.

    Formally,
    For a subarray Ai,Ai+1...Aj where 1 ≤ i < j ≤ N to be valid: LCM(Ai,Ai+1...Aj) should be equal to Ai*Ai+1*...*Aj. You have to print the size of the largest valid subarray.

    If no subarray satisfies output -1.

    Note:A single element is not considered a subarray according to definition in this problem.

    Input

    First line contains T, the number of testcases. Each testcase consists of N in one line followed by N integers in next line.

    Output

    For each testcase, print the required answer in one line.

    Constraints

    • 1T50
    • 2N105
    • 1Ai106

    Example

    Input:
    3
    2
    7 2
    4
    2 2 3 4
    3
    2 2 4
    
    Output:
    2
    2
    -1
    

    Explanation

    Example case 1.LCM(2,7)=2*7. Therefore, subarray A1 to A2 satisfies.

    Example case 2.The subarrays A2 to A3 and A3 to A4 are the maximum size possible.

    Example case 3.No subarray will satisfy.

    Warning: Use fast input/output. Large input files. Solutions may not pass in slower languages.

    Update: Time limit for python=10s

    给定序列, 求最长连续序列使得 lcm( Ax, ..... Ay ) = Ax*Ax+1*....*Ay .

    满足要求的时候 , Ax ~ Ay 这些数要符合, 他们的质因子没有重复。

    NlogN预处理质因子,dp出那个最右边的位置即可更新出答案 。~

    #include <bits/stdc++.h>
    using namespace std;
    const int N = 100010;
    const int M = 1000010;
    int n,e[N],pos[N],ans[N],to[M],f[M];
    bool not_pri[M] ;
    
    void init() {
        int tot = 0 ;
        for( int i = 2 ; i < M ; ++i ) if( !not_pri[i] ) {
            to[i] = ++tot; f[i] = i;
            for( int j = i + i ; j < M ; j += i ){
                not_pri[j] = true ; f[j] = i;
            }
        }
    }
    
    int Work( int num , int idx ) {
        int res = 0 ;
        while( num > 1 ){
            int tmp = f[num];
            if( pos[ to[tmp] ] ) res = max( res , pos[to[tmp]] );
            pos[ to[tmp] ] = idx ;
            while( num % tmp == 0 ) num /= tmp;
        }
        return res ;
    }
    
    void Run() {
        scanf("%d",&n);
        for( int i = 1 ; i <= n ; ++i ) scanf("%d",&e[i]);
        memset( pos , 0 , sizeof pos );
        for( int i = 1 ; i <= n ; ++i ) {
            ans[i] = max( ans[i-1] , Work( e[i] , i ) );
        }
        int res = 0 ;
        for( int i = 1 ; i <= n ; ++i ) res = max( res , i - ans[i] );
        if( res <= 1 ) puts("-1");
        else printf("%d
    ",res);
    }
    
    int main()
    {
    //    freopen("in.txt","r",stdin);
        init();
        int _ , cas = 1 ;
        scanf("%d",&_);
        while(_--)Run();
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/hlmark/p/4296786.html
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