'commit'

TangDou/AcWing/DP/ShuWei/HDU4734_Prepare.cpp

@@ -0,0 +1,35 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+/**
+12345-->f(12345)=1*2^4+2*2^3+3*2^2+4*2^1+5*2^0
+         f(1234) =1*2^3+2*2^2+3*2^1+4*2^0
+       2*f(1234) =1*2^4+2*2^3+3*2^2+4*2^1
+所以形成递归表示式
+*/
+//利用递归计算出F(x)
+int f(int x) {
+    if (x == 0) return 0;
+    return f(x / 10) * 2 + x % 10;
+}
+
+//利用循环进行计算
+int f2(int x) {
+    int res = 0;
+    int i = 0;
+    while (x) {
+        res += x % 10 * (1 << i);
+        i++;
+        x /= 10;
+    }
+    return res;
+}
+
+int main() {
+    cout << f(5) << endl;
+    cout << f2(12345) << endl;
+    //极大值是1e9-1=99999999
+    cout << f2(1e9 - 1) << endl;
+    //输出4599
+    return 0;
+}