move to left

library(data.table)
library(plyr)
library(dplyr)
library(magrittr)

dt = fread('No, A, B, C, D, E, F, G
1, 1, 3, 0, 0, 4, 2, 1
2, 1, 0, 0, 0, 2, 0, 3
3, 0, 1, 0, 3, 0, 0, 0
4, 1, 3, 2, 1, 0, 0, 0
5, 0, 6, 0, 0, 0, 0, 0
6, 0, 0, 0, 0, 2, 2, 1
')
dt %>% mutate(id=1:nrow(.)) %>% split(.$id) %>%
  llply(function(v){
    v = unlist(v)[1:(length(v)-1)]
    data.table(matrix(c(v[v!=0], rep(0, sum(v==0))), 1))
  }) %>% rbindlist %>% setnames(names(dt))