Title Description
Description
The CCC football match is a little different from the traditional football game, when a goal is scored in ascending order and only if the 4 players who have come into contact with the ball have the shirt number.
The player's shirt number is from 1 to 99, and each person's number is different.
Given the last scoring player's shirt number, please figure out how many legitimate combinations of players will be able to produce this goal.
Enter a description
Input Description
Enter an integer 1<=j<=99 that represents the player's shirt number
Output description
Output Description
The output has only one row and contains an integer that represents the number of combinations that make the player with the last goal numbered J.
Sample input
Sample Input
Sample Input 1:4
Sample Input 2:2
Sample Input 3:90
Sample output
Sample Output
Sample Output 1:1
Sample Output 2:0
Sample Output 3:113,564
Ideas:
This question test our permutation combination, but Ben Little did not learn this thing, but anyway, find the law everyone is will!
We can make a special judgment on this topic by the j<4, there is no answer
Since the requirement is four players, the first player's value range is 1~j-3, which means we can j-2,j-1,j the three players ignored, from the previous players to discuss.
F (4) =f (1+3) =1
F (5) =f (2+3) =2+1+1 = 2*1 + 1*2
F (6) =f (3+3) =3+2+1+2+1+1 = 3*1 + 2*2 + 1*3
F (7) =f (4+3) =4+3+2+1+3+2+1+2+1+1 = 4*1 + 3*2 + 2*3 + 1*4
So it's not hard to launch
F (i+3) =i*1+ (i-1) *2+ (i-2) *3+......+2* (i-1) +1*i
/*Super-Simple code*/#include<iostream>using namespacestd;Long Longans;intN;intMain () {CIN>>N; if(n<4) {cout<<0;return 0;} intk=n-3; for(intI=1, j=k;i<=k;i++,j--) ans+=i*J; cout<<ans;}
Don't pass me the ball.