add 9-4 Square

第9章搜索/9.2深度优先搜索/9-4Square.cpp

@@ -0,0 +1,76 @@
+#include <iostream>
+#include<cstring>
+#include<algorithm>
+#define MAXN 25
+using namespace std;
+
+int sticks[MAXN];
+bool visit[MAXN];
+
+int side;
+int m,n;
+bool DFS(int sum,int number,int position)
+{
+    if(number == 3)
+        return true;
+
+    int sample = 0;
+    for(int i = position; i<m; i++)
+    {
+        if( visit[i] || sum + sticks[i] > side || sticks[i] ==sample) continue;
+        visit[i] = true;
+        if( sum + sticks[i] == side)
+        {
+            if(DFS(0,number+1,0))return true;
+            else sample = sticks[i];
+        }
+        else
+        {
+            if(DFS(sum+sticks[i],number, i +1))return true;
+            else sample = sticks[i];
+        }
+        visit[i] = false;
+    }
+    return false;
+}
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin >> n;
+    while(n--)
+    {
+        int length = 0;
+        cin >> m;
+        for(int i=0; i<m; i++)
+        {
+            cin >> sticks[i];
+            length += sticks[i];
+        }
+        memset(visit,false,sizeof(visit));
+        if(length % 4 != 0)
+        {
+            cout<< "no\n";
+            continue;
+        }
+        side = length / 4;
+        sort(sticks,sticks+m,less<int>());
+        if(sticks[0] > side)
+        {
+            cout<< "no\n";
+            continue;
+        }
+        if(DFS(0,0,0))
+        {
+            cout << "yes\n";
+        }
+        else
+        {
+            cout << "no\n";
+        }
+
+
+    }
+
+
+    return 0;
+}