#include<windows.h>
#include<math.h>
#include<stdio.h>

int GetRoot(float a,float b,float c,double *root){
     double delta,deltasqrt;
     delta = b * b - 4.0 * a * c;
     if(delta < 0.0) return 0;
     deltasqrt = sqrt(delta);
     if(a != 0){
          root[0] = (-b + deltasqrt)/(2.0 * a);
          root[1] = (-b - deltasqrt)/(2.0 * a);
     }else{
          if(b != 0.0) root[0] = root[1] = -c/b;
          else return 0;
          if(root[0] == root[1]) return 1;
          else return 2;
     }
}

char str[80];
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR IpCmdLine,int nCmdShow){
     HWND hwnd;
     MSG msg;
     WNDCLASS wndclass;
     wndclass.style = CS_HREDRAW|CS_VREDRAW;
     wndclass.lpfnWndProc = WndProc;
     wndclass.cbClsExtra = 0;
     wndclass.cbWndExtra = 0;
     wndclass.hInstance = hInstance;
     wndclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
     wndclass.hCursor = LoadCursor(NULL,IDC_ARROW);
     wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
     wndclass.lpszMenuName = NULL;
     wndclass.lpszClassName = "SDKWin";
     if(!RegisterClass(&wndclass)){
          MessageBox(NULL,"REGISTER FAILSED!","HELLO WIN?",0);
          return 0;
     }
     hwnd = CreateWindow("SDKWin",
          "1.2.1--Windows API",
          WS_OVERLAPPEDWINDOW,
          CW_USEDEFAULT,
          CW_USEDEFAULT,
          CW_USEDEFAULT,
          CW_USEDEFAULT,
          NULL,
          NULL,
          hInstance,
          NULL);
     ShowWindow(hwnd,nCmdShow);
     UpdateWindow(hwnd);
     while(GetMessage(&msg,NULL,0,0)){
          TranslateMessage(&msg);
          DispatchMessage(&msg);
     }
     return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){
     HDC hdc;
     PAINTSTRUCT ps;
     static HWND hwndButton,hwndEdit;
     char strEdit[80],strA[3][80],strHint[80];
     float a[3];
     double root[2];
     int i,j,k,m;
     switch(message){
          case WM_CREATE: 
               hwndEdit = CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,10,60,200,25,hwnd,NULL,NULL,NULL);
               hwndButton = CreateWindow("button","解方程",WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,240,60,80,25,hwnd,NULL,NULL,NULL);
               return 0;
          case WM_COMMAND:
               if(((HWND)lParam==hwndButton)&&(HIWORD(wParam) == BN_CLICKED)){
                    GetWindowText(hwndEdit,strEdit,80);
                    k = 0;m = 0;
                    for(j = 0;j < 80;j++){
                         if(strEdit[j] == ','){
                              k++;m = 0;
                         }
                         else{
                              strA[k][m] = strEdit[j];m++;
                         }
                    }
                    for(i = 0;i < 3;i++){
                         a[i] = (float)atof(strA[i]);
                    }
                    int n = GetRoot(a[0],a[1],a[2],root);
                    if(n < 1) strcpy(str,"方程无根");
                    else sprintf(str,"方程解为：%f,%f",root[0],root[1]);
                    InvalidateRect(hwnd,NULL,TRUE);
               }
          case WM_PAINT:
               hdc = BeginPaint(hwnd,&ps);
               strcpy(strHint,"input三个二次方程的系数，中间逗号分隔");
               TextOut(hdc,10,40,strHint,strlen(strHint));
               TextOut(hdc,10,90,str,strlen(str));
               EndPaint(hwnd,&ps);
               return 0;
          case WM_DESTROY:
               PostQuitMessage(0);
               return 0;
     }
     return DefWindowProc(hwnd,message,wParam,lParam);
}