8.18早上

8.16/L-HarmonicNumber(II)/Readme.md

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+# L - Harmonic Number (II)
+* https://vjudge.net/contest/509210#problem/L
+### 题意
+res = res + n / i;求和，1 ≤ n < 2^31
+### 做法
+左右两部分考虑
+sqrt(n)前的直接求
+后面的按（n/2~1,n/3~n/2……,n/m)求
+特判m
+### 关键词
+
+### 易错点
+* 特判m
+### 工具箱
+* 

8.16/L-HarmonicNumber(II)/main.cpp

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+
+#include <iostream>
+#include<cstdio>
+#include<algorithm>
+#include <cmath>
+using namespace std;
+int main()
+{
+    long long t;
+    long long t1=0;
+    long long ans;
+    long long n;
+    long long now;
+    long long m;
+    scanf("%lld",&t);
+    while(t--)
+    {
+        scanf("%lld",&n);
+        ans=0;
+        m=sqrt(n);
+        for(long long i=1;i<=m; i++)
+        {
+            now=n/i-n/(i+1);
+            ans+=(i*now);
+            ans+=(n/i);
+        }
+        if(n/m==m)ans-=m;
+        printf("Case %lld: %lld\n",++t1,ans);
+    }
+    return 0;
+}