70. climbing stairs

public static int climbStairs(int n) {
	if(n == 0){
		return 0;
	}else if(n == 1){
		return 1;
	}else if(n ==2){
		return 2;
	}
	//dp[i]表示走i共有dp[i]种方法
	int[] dp = new int[n+1];
	dp[0] = 0;
	dp[1] = 1;
	dp[2] = 2;
	for(int i = 3; i < n+1; i++){
		dp[i] = dp[i-1] + dp[i-2];
	}
	return dp[n];
}