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// 70. Climbing Stairs
#include "leetcode.h"
/*
* you are climbinga staircase. it takes 'n' steps to reach the top. each time
* you can either climb one or two steps. in how many distinct ways can you
* climb to the top?
*/
double combination(int m, int n) {
if (!n || m == n)
return 1;
double res = 1;
for (int i = m; i > m - n; i--)
res *= i;
for (int i = n; i >= 1; i--)
res /= i;
return res;
}
int climbingStairs(int n) {
int one_step, two_step, total_step;
double method = 0;
for (int i = 0; i <= floor((double)n / 2); i++) {
two_step = i;
one_step = n - 2 * i;
total_step = one_step + two_step;
method += combination(total_step, one_step);
}
return (int)method;
}
int main() {
printf("%d\n", climbingStairs(2)); // expect: 2
printf("%d\n", climbingStairs(3)); // expect: 3
}
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