'commit'

TangDou/XiTi/1258.cpp

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+#include <bits/stdc++.h>
+
+using namespace std;
+
+// 递归
+// 分析：用树图进行分析，说明分枝多，重复多，计算多，速度慢，容易爆栈.从未知到已知，自我调用
+int louti(int n) {
+    if (n == 1) return 1;
+    if (n == 2) return 2;
+    return louti(n - 1) + louti(n - 2);
+}
+
+//递推
+// 分析：无多余运算，速度快，性能好，从已知至未知，推导
+int louti2(int n) {
+    int a = 1, b = 2, c = 0, i = 3;
+    if (n == 1) return a;
+    if (n == 2) return b;
+
+    while (i <= n) {
+        c = a + b;
+        a = b;
+        b = c;
+        i++;
+    }
+    return c;
+}
+
+int main() {
+    int n;
+    cin >> n;
+    //递归
+    cout << louti(n) << endl;
+    //递推
+    cout << louti2(n) << endl;
+    return 0;
+}