Why is my change to a range-for loop not work?

I'm at a loss. I am trying to sum two numbers of vector such that they equal target, then return their indices; however, when running the code with a C++11 for-loop, the result is incorrect. With vector [2,7,11,15] and target=9, the result for the C++11 loop is [0, 0]. Using the C-style loop, it is [0,1]. What gives?

class Solution {
public:
    vector<int> twoSumCstyle(vector<int>& nums, int target) {
        vector<int> sol(2);
        bool found = false;
        for (int i = 0; i< nums.size()-1; i++ ){
            for ( int x = i +1; x <nums.size(); x++){
                if (nums[i] + nums[x] == target) {
                    sol[0] = i;
                    sol[1] = x;
                    found = true;
                    break;
                }
            }
            if (found) break; 
        }
        return sol;  
    }

    vector<int> twoSumC11(vector<int>& nums, int target) {
        vector<int> sol(2);
        bool found = false;
        for (int i : nums ){
            for ( int x = i +1; x <nums.size(); x++){
                if (nums[i] + nums[x] == target) {
                    sol[0] = i;
                    sol[1] = x;
                    found = true;
                    break;
                }
            }
            if (found) break; 
        }
        return sol;  
    } 
};