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  1. library(data.table)
  2.  
  3. myunique <- function(df, verbose = FALSE) {
  4.     if (is.data.frame(df)) {
  5.         dt <- data.table(df)
  6.     } else if (is.data.table(df)) {
  7.         dt <- copy(df)
  8.     } else {
  9.         stop("Input should be a data.frame or a data.table")
  10.     }
  11.  
  12.     dt[, i := 1:.N]
  13.     dt[, x := as.character(x)]
  14.     dt[, y := as.character(y)]
  15.     dt_all <- rbind(
  16.         dt,
  17.         dt[, .(x = y, y = x, i = i)]
  18.     )
  19.  
  20.     # a dictionary x(character) -> index(integer)
  21.     dt_g1 <- dt_all[, .(i = list(i)), by = x]
  22.     setkey(dt_g1, x)
  23.  
  24.     # a dictionary index(integer) -> x(character)
  25.     dt_g2 <- dt_all[, .(x = list(x)), by = i]
  26.     dt_g2[, skip   := FALSE]
  27.     dt_g2[, select := FALSE]
  28.     setkey(dt_g2, i)
  29.  
  30.     while (TRUE) {
  31.         if (length(which(!dt_g2$skip)) > 0) {
  32.             # select first non-skipped index
  33.             cur_i  <- dt_g2[, min(which(!skip))]
  34.             if(verbose) message("current index:\t", cur_i, "/", nrow(dt_g2))
  35.             dt_g2[cur_i, select := TRUE]
  36.  
  37.             # get skipped index vector
  38.             cur_x  <- dt_g2[cur_i, x[[1]]]
  39.             skip_i <- dt_g1[cur_x, unique(do.call(c, i))]
  40.             dt_g2[skip_i, skip := TRUE]
  41.         } else {
  42.             break
  43.         }
  44.     }
  45.  
  46.     # return selected row
  47.     selected_idx <- dt_g2[select == TRUE, i]
  48.  
  49.     return(df[selected_idx, c("x", "y")])
  50. } 
  51.  
  52. cat("Input\n")
  53. df <- fread("x, y
  54. 	1, 2
  55. 	1, 3
  56. 	2, 4
  57. 	2, 6
  58. 	3, 2
  59. 	3, 7", header = TRUE)
  60. print(df)
  61.  
  62. cat("Output\n")
  63. myunique(df, verbose = FALSE)
  64.  
Success #stdin #stdout 0.46s 42520KB
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stdin
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Standard input is empty
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Input
   x y
1: 1 2
2: 1 3
3: 2 4
4: 2 6
5: 3 2
6: 3 7
Output
   x y
1: 1 2
2: 3 7
https://ideone.com/J1XkGl
language:
R (R 3.5.2)
created:
3 years ago
visibility:
public

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