更新了许多

数1的个数.cpp

@@ -0,0 +1,24 @@
+#include <iostream>
+#include <cmath>
+#include <cstdlib>
+#include <cstdio>
+#include <iomanip>
+using namespace std;
+int main(){
+	int a;
+	int b=0;
+	cin >>a;
+	for(int i=1;i<=a;i++){
+		int j=i;
+		while(j){
+			if(j%10==1){
+			b++;
+			}
+			j/=10;
+		}
+	}
+	cout <<b;
+	return 0;
+}
+
+