ZOJ 1629 Counting Triangles（数学题 递推）

Counting Triangles

---

Time Limit: 2 Seconds      Memory Limit: 65536 KB

---

Given an equilateral triangle with n the length of its side, program to count how many triangles in it.

Input

The length n (n <= 500) of the equilateral triangle's side, one per line.

process to the end of the file

Output

The number of triangles in the equilateral triangle, one per line.

Sample Input

1
2
3

Sample Output

1
5
13

 

如果说所有的递推都是动态规划，那这是最简单的动态规划了

# include<stdio.h>
int n;
int f[501];
void init(){
    int i,j;
    f[0]=0;
    for(i=1;i<501;i++)
        f[i]=f[i-1]+i*(i/2)+i*(i+1)/2-(i/2)*(i/2);
}
int main(){
    init();
    while(scanf("%d",&n)!=EOF)
        printf("%d\n",f[n]);
    return 0;
}