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  1. /*
  2.     File: rectangles.cpp
  3.     
  4.     Compile command: g++ -O2 -std=c++17 -Wall -Wextra -pedantic rectangles.cpp -o rectangles.o
  5.     
  6.     Example:
  7.     4 3
  8.     ###
  9.     #.#
  10.     #.#
  11.     ###
  12.     
  13.     Output: 1
  14. */
  15.  
  16. #pragma GCC diagnostic ignored "-Wunused-result"
  17. #include <stdio.h>
  18. #include <cassert>
  19. #include <cstdlib>
  20. #include <ctime>
  21. #include <cstdint>
  22.  
  23. const bool TIMING = true;
  24.  
  25. char getChar() {
  26.     static char buffer[1024*1024];
  27.     static int pos = 0;
  28.     static int size = 0;
  29.     if (pos == size) {
  30.         size = fread(buffer, 1, 1024*1024, stdin);
  31.         pos = 0;
  32.     }
  33.     if (pos == size) {
  34.         return EOF;
  35.     }
  36.     return buffer[pos++];
  37. }
  38.  
  39. void putChar(char c) {
  40. // c == -1 or size == sizeof(buffer) --> flush buffer
  41.     static char buffer[1024*1024];
  42.     static int size = 0;
  43.     if (size == 1024 * 1024 || c == -1) {
  44.         fwrite(buffer, 1, size, stdout);
  45.         size = 0;
  46.     }
  47.     buffer[size++] = c;
  48. }
  49.  
  50. int getInt(bool& success) {
  51.     char c = '?';
  52.     while (!(c == '-' || ('0' <= c && c <= '9') || c == EOF)) {
  53.         c = getChar();
  54.     }
  55.     if (c == EOF) {
  56.         success = false;
  57.         return 0;
  58.     }
  59.     int sign = 1;
  60.     if (c == '-') {
  61.         sign *= -1;
  62.         c = getChar();
  63.     }
  64.     int answ = 0;
  65.     while ('0' <= c && c <= '9') {
  66.         (answ *= 10) += (c-'0');
  67.         c = getChar();
  68.     }
  69.     success = true;
  70.     return sign * answ;
  71. }
  72.  
  73. void putStr(const char *buf) {
  74.     for (auto it = buf; *it != '\0'; ++it) {
  75.         putChar(*it);
  76.     }
  77. }
  78.  
  79. void putInt(int number) {
  80.     static char buf[12];
  81.     sprintf(buf, "%d", number);
  82.     putStr(buf);
  83. }
  84.  
  85. void putInt(long long number) {
  86.     static char buf[24];
  87.     sprintf(buf, "%lld", number);
  88.     putStr(buf);
  89. }
  90.  
  91. int main() {
  92.     double total_time = clock();
  93.     for (int id = 0; id < 100; ++id) {
  94.         int nRows = 350; // input number of rows of array
  95.         int nCols = 350; // input number of cols of array
  96.  
  97.         static char arr[350][350]; // arr[r][c] = 1 if '#' and arr[r][c] = 0 if '.'
  98.         for (int row = 0; row < nRows; ++row) {
  99.             for (int col = 0; col < nCols; ++col) {
  100.                 char c = '#'; // char c = getChar();
  101.                 arr[row][col] = (c == '#');
  102.             }
  103.             char c = '\n'; // char c = getChar();
  104.             assert(c == '\n' || (c == EOF && row == nRows-1));
  105.         }
  106.  
  107.         static int maxLenDown[351][350]; // maxLenDown[r][c] = len of max sequence of '#' from pos (row, col) in side of increasing row
  108.         for (int row = 0; row <= nRows; ++row) {
  109.             for (int col = 0; col < nCols; ++col) {
  110.                 maxLenDown[row][col] = 0;
  111.             }
  112.         }
  113.  
  114.         for (int row = nRows-1; row >= 0; --row) {
  115.             for (int col = 0; col < nCols; ++col) {
  116.                 if (arr[row][col]) {
  117.                     maxLenDown[row][col] = 1 + maxLenDown[row+1][col];
  118.                 }
  119.             }
  120.         }        
  121.  
  122.         static int bin_2[351]; // bin_2[i] = C(i, 2);
  123.         for (int i = 0; i < 351; ++i) {
  124.             bin_2[i] = i * (i-1) / 2;
  125.         }
  126.  
  127.         // Calculate all rectangles with top side = row1 and bottom side = row2 (rectangles with width = 2 will also be counted)
  128.         long long answ = 0;
  129.         for (int row1 = 0; row1 < nRows-2; ++row1) {
  130.             int temp = 0;
  131.             for (int row2 = row1+2; row2 < nRows; ++row2) {
  132.                 int len = 0;
  133.                 for (int col = 0; col < nCols; ++col) { // TO DO: speed up this cycle
  134.                     if (arr[row1][col] & arr[row2][col]) {
  135.                         len += (maxLenDown[row1][col] >= row2-row1+1);
  136.                     } else {
  137.                         temp += bin_2[len];
  138.                         len = 0;
  139.                     }
  140.                 }
  141.                 temp += bin_2[len];
  142.             }
  143.             answ += temp;
  144.         }
  145.         // Decreasing number of rectangles with width = 2
  146.         for (int col1 = 0; col1 < nCols-1; ++col1) {
  147.             const int col2 = col1+1;
  148.             int len = 0;
  149.             for (int row = 0; row < nRows; ++row) {
  150.                 if (arr[row][col1] & arr[row][col2]) {
  151.                     ++len;
  152.                 } else {
  153.                     if (len >= 3) {
  154.                         answ -= bin_2[len-1];
  155.                     }
  156.                     len = 0;
  157.                 }
  158.             }
  159.             if (len >= 3) {
  160.                 answ -= bin_2[len-1];
  161.             }
  162.         }
  163.  
  164.         putInt(answ);
  165.         putChar('\n');
  166.     }
  167.     putChar(-1);
  168.  
  169.     if (TIMING) {
  170.         total_time = (clock() - total_time) / CLOCKS_PER_SEC;
  171.         printf("----------------\ntime = %0.3f\n", total_time);
  172.     }
  173.  
  174.     return 0;
  175. }
Success #stdin #stdout 1.72s 4376KB
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----------------
time = 1.720
https://ideone.com/PrAmnJ
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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