diff --git a/cpp/algorithms/problem1.cpp b/cpp/algorithms/problem1.cpp
index e69de29..e9cfdb5 100644
--- a/cpp/algorithms/problem1.cpp
+++ b/cpp/algorithms/problem1.cpp
@@ -0,0 +1,23 @@
+//http://acm.hdu.edu.cn/showproblem.php?pid=2000
+#include <cstdio>
+
+void sort_and_output(char * str){
+    for(int i=0;i<3;i++){
+        for(int j=i+1;j<3;j++){
+            if(str[i]>str[j]){
+                char tmp=str[j];
+                str[j]=str[i];
+                str[i]=tmp;
+            }
+        }
+    }
+    printf("%c %c %c\n",str[0],str[1],str[2]);
+}
+
+int main(int argc,char ** argv){
+    char str[3];
+    while(scanf("%s",str)!=EOF){
+        sort_and_output(str);
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/cpp/algorithms/problem2.cpp b/cpp/algorithms/problem2.cpp
new file mode 100644
index 0000000..b8c123c
--- /dev/null
+++ b/cpp/algorithms/problem2.cpp
@@ -0,0 +1,11 @@
+//http://acm.hdu.edu.cn/showproblem.php?pid=2001
+#include <cstdio>
+#include <cmath>
+
+int main(int argc,char ** argv){
+    double x1,y1,x2,y2;
+    while(scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2)!=EOF){
+        printf("%.2f\n",sqrt(pow(x1-x2,2)+pow(y1-y2,2)));
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/cpp/algorithms/problem3.cpp b/cpp/algorithms/problem3.cpp
new file mode 100644
index 0000000..c021742
--- /dev/null
+++ b/cpp/algorithms/problem3.cpp
@@ -0,0 +1,11 @@
+//http://acm.hdu.edu.cn/showproblem.php?pid=2002
+#include <cstdio>
+#define PI 3.1415927
+
+int main(int argc,char ** argv){
+    double r;
+    while(scanf("%lf",&r)!=EOF){
+        printf("%.3f\n",4.0/3.0*r*r*r*PI);
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/cpp/algorithms/problem4.cpp b/cpp/algorithms/problem4.cpp
new file mode 100644
index 0000000..858ba26
--- /dev/null
+++ b/cpp/algorithms/problem4.cpp
@@ -0,0 +1,10 @@
+//http://acm.hdu.edu.cn/showproblem.php?pid=2003
+#include <cstdio>
+
+int main(int argc,char ** argv){
+    double x;
+    while(scanf("%lf",&x)!=EOF){
+        printf("%.2f\n",x>0?x:-x);
+    }
+    return 0;
+}
\ No newline at end of file