public int Fibonacci(int n) {
if(n==0) return 0;
if(n==1) return 1;
return Fibonacci(n-1)+Fibonacci(n-2);
}
递归时间复杂度高
public int Fibonacci(int n) {
if(n==0)return 0;
if(n==1)return 1;
int fn1=0,fn2=1;
int res = 0;
for(int i=2;i<=n;i++){
res = fn1+fn2;
fn1 = fn2;
fn2 = res;
}
return res;
}
时间复杂度O(n)
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