24a-section-4-solutions

24a-section-4-solutions - Mehran Sahami CS 106A Handout#24A...

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Unformatted text preview: Mehran Sahami CS 106A Handout #24A October 24, 2007 Solution to Section #4 Portions of this handout by Eric Roberts and Patrick Young 1. Adding commas to numeric strings private String addCommasToNumericString(String digits) { String result = ""; int len = digits.length(); int nDigits = 0; for (int i = len - 1; i >= 0; i--) { result = digits.charAt(i) + result; nDigits++; if (((nDigits % 3) == 0) && (i > 0)) { result = "," + result; } } return result; } 2. Deleting characters from a string private String removeAllOccurrences(String str, char ch) { String result = ""; for (int i = 0; i < str.length(); i++) { if (str.charAt(i) != ch) { result += str.charAt(i); } } return result; } A slightly different approach that involves a while loop instead of a for loop: private String removeAllOccurrences(String str, char ch) { while (true) { int pos = str.indexOf(ch); if (pos >= 0) { str = str.substring(0, pos) + str.substring(pos + 1); } else break; } return str; } Could you generalize these functions to remove substrings? For instance, removeAllSubstrings("Mississippi", 'si') returns "Missppi". Would these two functions ever return different values for the same input? –2– 3. Heap/Stack diagrams heap 1000 num den num den num den num den num den 1 2 1020 1 1 1040 1 2 1060 garbage i result n x 1080 1 4 1 8 stack 3 1080 3 1000 1000 FFB0 FFB4 FFB8 FFB8 r FFC0 4. Tracing method execution ...
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