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f2.c

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+#include <stdio.h>
+#include <time.h>
+#include <stdlib.h>
+#include <string.h>
+int used[10];
+
+void row(int row[]){
+    int nums[3];
+    int numcount=0;
+    while(numcount < 3){
+        int num=rand()%9+1;
+        if(!used[num]){
+            nums[numcount++]=num; 
+            used[num]=1;
+        }
+    }
+    int i; 
+    for ( i=0;i < 3; i++) {
+        int index;
+        do{
+            index=rand()%9;
+    		}while(row[index] != 0);
+    row[index]=nums[i];
+    }
+}
+int main(){
+	int i,j;
+    int a[10][10];
+    srand((unsigned)time(NULL));
+    for ( i = 0; i < 9; i++){
+        for( j=0; j < 9; j++){
+            a[i][j]=0;
+        }
+				if(i % 3 == 0) 
+					memset(used, 0, sizeof(used)); 
+        row(a[i]);
+    }
+   
+    for(i=0;i < 9;i++){
+        for( j=0;j < 9;j++) {
+            printf("%d ",a[i][j]);
+            
+        }
+       printf("\n"); 
+    }
+    return 0;
+}