Problem 23 (#43)

fix link typo for trapping rain water

Problem 42 (#42)

Problem 39 (#41)

Problem 33 (#40)

Problem 994 (#39)

Problem 200 (#38)

Problem 98 (#37)

Problem 155 (#36)

Problem 238 (#35)

Problem 322 (#34)

Problem 208 (#33)

Problem 207 (#32)

Problem 146 (#31)

add solution and links from problem-253