cppType errorMedium

std::string::find comparison with signed integer

Time: 0:00

BugFind the bug and fix the code

What it should do

Find substring index in text, or return -1 if missing. Example: findSubstrPosition("hello world", "world") -> 6

What happens instead

Missing substring returns false positive index due to npos integer overflow

#include <iostream>
#include <string>

int findSubstrPosition(std::string text, std::string target) {
    // std::string::find returns size_t. Storing into signed int overflows on npos
    int pos = text.find(target);
    if (pos >= 0) {
        return pos;
    }
    return -1;
}

int main() {
    std::cout << findSubstrPosition("hello world", "world") << std::endl;
    return 0;
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the type errors pattern

Totals that concatenate, sorts that put 10 before 9, comparisons that refuse to run.

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#include <iostream> #include <string> int findSubstrPosition(std::string text, std::string target) { // std::string::find returns size_t. Storing into signed int overflows on npos int pos = text.find(target); if (pos >= 0) { return pos; } return -1; } int main() { std::cout << findSubstrPosition("hello world", "world") << std::endl; return 0; }

std::string::find comparison with signed integer

What it should do

What happens instead

More type errors to practise

std::string::find comparison with signed integer

What it should do

What happens instead

More type errors to practise