Develop a solution to change Roman numerals into their decimal equivalents.

Consider all possibilities of Roman numerals$$no letters, only one, two, etc. Assume that the Roman numerals are in the correct order. One Roman numeral character is entered at a time. The Roman numeral is entered from left to right. Roman numeral equivalents are as follows:

I $=1$

V$=5$

X$=10$

L$=50$

C$=100$

D$=500$

M$=1000$

Examples of input numbers are IV$,$ XIX, MMCDXL$,$ and CCLV$.$ The solution must be presented using Straight, Positive, Negative and Switch and Case logic structure whit it respective flowchart and pseudocodes.