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DOUBT IN VECTORS
By Akpr, history, 4 years ago, In English

Dear community Why the output of below code is not -1 ?

CODE --------------------------

include<bits/stdc++.h>

using namespace std;

int main(){ vector v; cout << v.size() — 1 << endl;

}

RECIEVED OUTPUT => 4294967295 but not -1

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4 years ago, hide # |
 
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Auto comment: topic has been updated by Akpr (previous revision, new revision, compare).

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4 years ago, hide # |
 
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v.size() gives unsigned_int.

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4 years ago, hide # |
 
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Because v.size() is size_t which is unsigned type (width of type is implementation-defined).
v.size() - 1 = (0 :: size_t) - (1 :: int) = [1 casting to wider type size_t] = (0 :: size_t) - (1 :: size_t) = (2^b - 1 :: size_t) [b - size of size_t in bytes].

In other words, unsigned overflow was happen.

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